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[GitHub] [incubator-mxnet] barry-jin opened a new pull request #20473: [v2.0][DOC] Add migration guide
barry-jin opened a new pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473
## Description ##
Add Migration Guide
## Comments ##
- If this change is a backward incompatible change, why must this change be made.
- Interesting edge cases to note here
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[GitHub] [incubator-mxnet] barry-jin commented on pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
barry-jin commented on pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473#issuecomment-902061113
@mxnet-bot run ci [windows-gpu]
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[GitHub] [incubator-mxnet] mxnet-bot commented on pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
mxnet-bot commented on pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473#issuecomment-902061378
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[GitHub] [incubator-mxnet] mxnet-bot commented on pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
mxnet-bot commented on pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473#issuecomment-890217696
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[GitHub] [incubator-mxnet] barry-jin merged pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
barry-jin merged pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473
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[GitHub] [incubator-mxnet] barry-jin commented on pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
barry-jin commented on pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473#issuecomment-890217661
@mxnet-bot run ci [website, unix-gpu]
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[GitHub] [incubator-mxnet] barry-jin commented on pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
barry-jin commented on pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473#issuecomment-904211061
@szha Thanks for the suggestions! I have updated the migration guide.
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[GitHub] [incubator-mxnet] mxnet-bot commented on pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
mxnet-bot commented on pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473#issuecomment-889301343
Hey @barry-jin , Thanks for submitting the PR
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[GitHub] [incubator-mxnet] szha commented on a change in pull request #20473: [v2.0][DOC] Add migration guide
Posted by GitBox <gi...@apache.org>.
szha commented on a change in pull request #20473:
URL: https://github.com/apache/incubator-mxnet/pull/20473#discussion_r694319553
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
Review comment:
```suggestion
Since the introduction of the Gluon API in MXNet 1.x, it has superseded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in the deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
Review comment:
```suggestion
- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create a graph.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
+
+
+### NumPy-compatible Programming Experience
+#### NumPy Arrays
+MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that needs attention, as mentioned below.
+**Migration Guide**:
+
+1. Currently, NumPy ndarray only supports `default` storage type, other storage types, like `row_sparse`, `csr` are not supported. Also, `tostype()` attribute is deprecated.
+
+2. Users can use `as_np_ndarray` attribute to switch from a legacy NDArray to NumPy ndarray just like this:
+ ```{.python}
+ import mxnet as mx
+ nd_array = mx.ones((5,3))
+ np_array = nd_array.as_np_ndarray()
+ ```
+
+3. Compared with legacy NDArray, some attributes are deprecated in NumPy ndarray. Listed below are some of the deprecated APIs and their corresponding replacements in NumPy ndarray, others can be found in [**Appendix/NumPy Array Deprecated Attributes**](#NumPy-Array-Deprecated-Attributes).
+ | Deprecated Attributes | NumPy ndarray Equivalent |
+ | ----------------------------------------------------- | ------------------------------ |
+ | `a.asscalar()` | `a.item()` |
+ | `a.as_in_context()` | `a.as_in_ctx()` |
+ | `a.context` | `a.ctx` |
+ | `a.reshape_like(b)` | `a.reshape(b.shape)` |
+ | `a.zeros_like(b)` | `mx.np.zeros_like(b)` |
+ | `a.ones_like(b)` | `mx.np.ones_like(b)` |
+
+4. Compared with legacy NDArray, some attributes will have different behaviors and take different inputs.
+ | Attribute | Legacy Inputs | NumPy Inputs |
+ | ----------------------------- | ------------------------ | -------- |
+ | `a.reshape(*args, **kwargs)` | **shape**: Some dimensions of the shape can take special values from the set {0, -1, -2, -3, -4}. <br> The significance of each is explained below: <br> ``0`` copy this dimension from the input to the output shape. <br> ``-1`` infers the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy all/remainder of the input dimensions to the output shape. <br> ``-3`` use the product of two consecutive dimensions of the input shape as the output dimension. <br> ``-4`` split one dimension of the input into two dimensions passed subsequent to -4 in shape (can contain -1). <br> **reverse**: If set to 1, then the special values are inferred from right to left | **shape**: shape parameter will be **positional argument** rather than key-word argument. <br> Some dimensions of the shape can take special values from the set {-1, -2, -3, -4, -5, -6}. <br> The significance of each is explained below: <br> ``-1`` infers
the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy this dimension from the input to the output shape. <br> ``-3`` will skip current dimension if and only if the current dim size is one. <br> ``-4`` copy all remain of the input dimensions to the output shape. <br> ``-5`` use the product of two consecutive dimensions of the input shape as the output. <br> ``-6`` split one dimension of the input into two dimensions passed subsequent to -6 in the new shape. <br> **reverse**: No **reverse** parameter for `np.reshape` but for `npx.reshape`. <br> **order**: Read the elements of `a` using this index order, and place the elements into the reshaped array using this index order. |
+
+
+#### NumPy and NumPy-extension Operators
+Most of the legacy NDArray operators(`mx.nd.op`) have the equivalent ones in np/npx namespace, users can just repalce them with `mx.np.op` or `mx.npx.op` to migrate. Some of the operators will have different inputs and behaviors as listed in the table below.
Review comment:
```suggestion
Most of the legacy NDArray operators(`mx.nd.op`) have the equivalent ones in np/npx namespace. Users can just replace them with `mx.np.op` or `mx.npx.op` to migrate. Some of the operators will have different inputs and behaviors as listed in the table below.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
+
+
+### NumPy-compatible Programming Experience
+#### NumPy Arrays
+MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that needs attention, as mentioned below.
+**Migration Guide**:
+
+1. Currently, NumPy ndarray only supports `default` storage type, other storage types, like `row_sparse`, `csr` are not supported. Also, `tostype()` attribute is deprecated.
+
+2. Users can use `as_np_ndarray` attribute to switch from a legacy NDArray to NumPy ndarray just like this:
+ ```{.python}
+ import mxnet as mx
+ nd_array = mx.ones((5,3))
+ np_array = nd_array.as_np_ndarray()
+ ```
+
+3. Compared with legacy NDArray, some attributes are deprecated in NumPy ndarray. Listed below are some of the deprecated APIs and their corresponding replacements in NumPy ndarray, others can be found in [**Appendix/NumPy Array Deprecated Attributes**](#NumPy-Array-Deprecated-Attributes).
+ | Deprecated Attributes | NumPy ndarray Equivalent |
+ | ----------------------------------------------------- | ------------------------------ |
+ | `a.asscalar()` | `a.item()` |
+ | `a.as_in_context()` | `a.as_in_ctx()` |
+ | `a.context` | `a.ctx` |
+ | `a.reshape_like(b)` | `a.reshape(b.shape)` |
+ | `a.zeros_like(b)` | `mx.np.zeros_like(b)` |
+ | `a.ones_like(b)` | `mx.np.ones_like(b)` |
+
+4. Compared with legacy NDArray, some attributes will have different behaviors and take different inputs.
+ | Attribute | Legacy Inputs | NumPy Inputs |
+ | ----------------------------- | ------------------------ | -------- |
+ | `a.reshape(*args, **kwargs)` | **shape**: Some dimensions of the shape can take special values from the set {0, -1, -2, -3, -4}. <br> The significance of each is explained below: <br> ``0`` copy this dimension from the input to the output shape. <br> ``-1`` infers the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy all/remainder of the input dimensions to the output shape. <br> ``-3`` use the product of two consecutive dimensions of the input shape as the output dimension. <br> ``-4`` split one dimension of the input into two dimensions passed subsequent to -4 in shape (can contain -1). <br> **reverse**: If set to 1, then the special values are inferred from right to left | **shape**: shape parameter will be **positional argument** rather than key-word argument. <br> Some dimensions of the shape can take special values from the set {-1, -2, -3, -4, -5, -6}. <br> The significance of each is explained below: <br> ``-1`` infers
the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy this dimension from the input to the output shape. <br> ``-3`` will skip current dimension if and only if the current dim size is one. <br> ``-4`` copy all remain of the input dimensions to the output shape. <br> ``-5`` use the product of two consecutive dimensions of the input shape as the output. <br> ``-6`` split one dimension of the input into two dimensions passed subsequent to -6 in the new shape. <br> **reverse**: No **reverse** parameter for `np.reshape` but for `npx.reshape`. <br> **order**: Read the elements of `a` using this index order, and place the elements into the reshaped array using this index order. |
+
+
+#### NumPy and NumPy-extension Operators
+Most of the legacy NDArray operators(`mx.nd.op`) have the equivalent ones in np/npx namespace, users can just repalce them with `mx.np.op` or `mx.npx.op` to migrate. Some of the operators will have different inputs and behaviors as listed in the table below.
+**Migration Guide**:
+
+1. Operators migration with name/inputs changes
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.flatten(*args, **kwargs)` | `mx.npx.batch_flatten(*args, **kwargs)` | moved to `npx` namespace with new name `batch_flatten` |
+ | `mx.nd.concat(a, b, c)` | `mx.np.concatenate([a, b, c])` | - moved to `np` namespace with new name `concatenate`. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.stack(a, b, c)` | `mx.np.stack([a, b, c])` | - moved to `np` namespace. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.SliceChannel(*args, **kwargs)` | `mx.npx.slice_channel(*args, **kwargs)` | - moved to `npx` namespace with new name `slice_channel`. |
+ | `mx.nd.FullyConnected(*args, **kwargs)` | `mx.npx.fully_connected(*args, **kwargs)` | - moved to `npx` namespace with new name `fully_connected`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.elemwise_add(a, b)` | `a + b` | - Just use ndarray python operator. |
+ | `mx.nd.elemwise_mul(a, b)` | `mx.np.multiply(a, b)` | - Use `multiply` operator in `np` namespace. |
+
+2. Operators migration with multiple steps: `mx.nd.mean` -> `mx.np.mean`:
+```{.python}
+import mxnet as mx
+# Legacy: calculate mean value with reduction on axis 1
+# with `exclude` option on
+nd_mean = mx.nd.mean(data, axis=1, exclude=1)
+
+# Numpy: no exclude option to users, but user can perform steps as follow
+axes = list(range(data.ndim))
+del axes[1]
+np_mean = mx.np.mean(data, axis=axes)
+```
+
+3. Random Operators
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ---------------------------- |
+ | `mx.random.uniform(-1.0, 1.0, shape=(2, 3))` <br> `mx.nd.random.uniform(-1.0, 1.0, shape=(2, 3))` | `mx.np.random.uniform(-1.0, 1.0, size=(2, 3))` | For all the NumPy random operators, use **size** key word instead of **shape** |
Review comment:
```suggestion
| `mx.random.uniform(-1.0, 1.0, shape=(2, 3))` <br> `mx.nd.random.uniform(-1.0, 1.0, shape=(2, 3))` | `mx.np.random.uniform(-1.0, 1.0, size=(2, 3))` | For all the NumPy random operators, use **size** keyword instead of **shape** |
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
+
+
+### NumPy-compatible Programming Experience
+#### NumPy Arrays
+MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that needs attention, as mentioned below.
+**Migration Guide**:
+
+1. Currently, NumPy ndarray only supports `default` storage type, other storage types, like `row_sparse`, `csr` are not supported. Also, `tostype()` attribute is deprecated.
+
+2. Users can use `as_np_ndarray` attribute to switch from a legacy NDArray to NumPy ndarray just like this:
+ ```{.python}
+ import mxnet as mx
+ nd_array = mx.ones((5,3))
+ np_array = nd_array.as_np_ndarray()
+ ```
+
+3. Compared with legacy NDArray, some attributes are deprecated in NumPy ndarray. Listed below are some of the deprecated APIs and their corresponding replacements in NumPy ndarray, others can be found in [**Appendix/NumPy Array Deprecated Attributes**](#NumPy-Array-Deprecated-Attributes).
+ | Deprecated Attributes | NumPy ndarray Equivalent |
+ | ----------------------------------------------------- | ------------------------------ |
+ | `a.asscalar()` | `a.item()` |
+ | `a.as_in_context()` | `a.as_in_ctx()` |
+ | `a.context` | `a.ctx` |
+ | `a.reshape_like(b)` | `a.reshape(b.shape)` |
+ | `a.zeros_like(b)` | `mx.np.zeros_like(b)` |
+ | `a.ones_like(b)` | `mx.np.ones_like(b)` |
+
+4. Compared with legacy NDArray, some attributes will have different behaviors and take different inputs.
+ | Attribute | Legacy Inputs | NumPy Inputs |
+ | ----------------------------- | ------------------------ | -------- |
+ | `a.reshape(*args, **kwargs)` | **shape**: Some dimensions of the shape can take special values from the set {0, -1, -2, -3, -4}. <br> The significance of each is explained below: <br> ``0`` copy this dimension from the input to the output shape. <br> ``-1`` infers the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy all/remainder of the input dimensions to the output shape. <br> ``-3`` use the product of two consecutive dimensions of the input shape as the output dimension. <br> ``-4`` split one dimension of the input into two dimensions passed subsequent to -4 in shape (can contain -1). <br> **reverse**: If set to 1, then the special values are inferred from right to left | **shape**: shape parameter will be **positional argument** rather than key-word argument. <br> Some dimensions of the shape can take special values from the set {-1, -2, -3, -4, -5, -6}. <br> The significance of each is explained below: <br> ``-1`` infers
the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy this dimension from the input to the output shape. <br> ``-3`` will skip current dimension if and only if the current dim size is one. <br> ``-4`` copy all remain of the input dimensions to the output shape. <br> ``-5`` use the product of two consecutive dimensions of the input shape as the output. <br> ``-6`` split one dimension of the input into two dimensions passed subsequent to -6 in the new shape. <br> **reverse**: No **reverse** parameter for `np.reshape` but for `npx.reshape`. <br> **order**: Read the elements of `a` using this index order, and place the elements into the reshaped array using this index order. |
+
+
+#### NumPy and NumPy-extension Operators
+Most of the legacy NDArray operators(`mx.nd.op`) have the equivalent ones in np/npx namespace, users can just repalce them with `mx.np.op` or `mx.npx.op` to migrate. Some of the operators will have different inputs and behaviors as listed in the table below.
+**Migration Guide**:
+
+1. Operators migration with name/inputs changes
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.flatten(*args, **kwargs)` | `mx.npx.batch_flatten(*args, **kwargs)` | moved to `npx` namespace with new name `batch_flatten` |
+ | `mx.nd.concat(a, b, c)` | `mx.np.concatenate([a, b, c])` | - moved to `np` namespace with new name `concatenate`. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.stack(a, b, c)` | `mx.np.stack([a, b, c])` | - moved to `np` namespace. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.SliceChannel(*args, **kwargs)` | `mx.npx.slice_channel(*args, **kwargs)` | - moved to `npx` namespace with new name `slice_channel`. |
+ | `mx.nd.FullyConnected(*args, **kwargs)` | `mx.npx.fully_connected(*args, **kwargs)` | - moved to `npx` namespace with new name `fully_connected`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.elemwise_add(a, b)` | `a + b` | - Just use ndarray python operator. |
+ | `mx.nd.elemwise_mul(a, b)` | `mx.np.multiply(a, b)` | - Use `multiply` operator in `np` namespace. |
+
+2. Operators migration with multiple steps: `mx.nd.mean` -> `mx.np.mean`:
+```{.python}
+import mxnet as mx
+# Legacy: calculate mean value with reduction on axis 1
+# with `exclude` option on
+nd_mean = mx.nd.mean(data, axis=1, exclude=1)
+
+# Numpy: no exclude option to users, but user can perform steps as follow
+axes = list(range(data.ndim))
+del axes[1]
+np_mean = mx.np.mean(data, axis=axes)
+```
+
+3. Random Operators
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ---------------------------- |
+ | `mx.random.uniform(-1.0, 1.0, shape=(2, 3))` <br> `mx.nd.random.uniform(-1.0, 1.0, shape=(2, 3))` | `mx.np.random.uniform(-1.0, 1.0, size=(2, 3))` | For all the NumPy random operators, use **size** key word instead of **shape** |
+ | `mx.nd.random.multinomial(*args, **kwargs)` | `mx.npx.random.categorical(*args, **kwargs)` | [use `npx.random.categorical` to have the behavior of drawing 1 sample from multiple distributions.](https://github.com/apache/incubator-mxnet/issues/20373#issuecomment-869120214) |
+
+4. Control Flow Operators
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.contrib.foreach(body, data, init_states, name)` | `mx.npx.foreach(body, data, init_states, name)` | - moved to `npx` namespace. <br> - Will not support global variables as body's inputs(body's inputs must be either data or states or both) |
+ | `mx.nd.contrib.while_loop(cond, func, loop_vars, max_iterations, name)` | `mx.npx.while_loop(cond, func, loop_vars, max_iterations, name)` | - moved to `npx` namespace. <br> - Will not support global variables as cond or func's inputs(cond or func's inputs must be in loop_vars) |
+ | `mx.nd.contrib.cond(pred, then_func, else_func, inputs, name)` | `mx.npx.cond(pred, then_func, else_func, name)` | - moved to `npx` namespace. <br> - users needs to provide the inputs of pred, then_func and else_func as inputs <br> - Will not support global variables as pred, then_func or else_func's inputs(pred, then_func or else_func's inputs must be in inputs) |
+
+5. Functionalities
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.save(*args, **kwargs)` | `mx.npx.savez(*args, **kwargs)` | - moved to `npx` namespace. <br> - Only accept positional arguments, try to flatten the list/dict before feed in |
+ | `mx.nd.load(*args, **kwargs)` | `mx.npx.load(*args, **kwargs)` | - moved to `npx` namespace. |
+ | `mx.nd.waitall()` | `mx.npx.waitall()` | - moved to `npx` namespace. |
+
+Other operator changes are included in [**Appendix/NumPy and NumPy-extension Operators**](#NumPy-and-NumPy-extension-Operators1)
+
+
+
+### Layers and Blocks
+With deferred compute and tracing being introduced in Gluon2.0, users do not need to interact with symbols any more. There are a lot of changes in building a model with Gluon API, including parameter management and naming, forward pass computing and parameter shape inferencing. We will provide a step-by-step migration guidance on how to build a model with new APIs.
+
+#### Parameter Management and Block Naming
+In Gluon, each Parameter or Block has a name (and prefix). Parameter names are specified by users and Block names can be either specified by users or automatically created. In Gluon 1.x, parameters are accessed via the `params` variable of the `ParameterDict` in `Block`. Users will need to manually use `with self.name_scope():` for children blocks and specify prefix for the top level block. Otherwise, it will lead to wrong name scopes and can return parameters of children blocks that are not in current name scope. An example for initializing the Block and Parameter in Gluon 1.x:
Review comment:
```suggestion
In Gluon, each Parameter or Block has a name (and prefix). Parameter names are specified by users and Block names can be either specified by users or automatically created. In Gluon 1.x, parameters are accessed via the `params` variable of the `ParameterDict` in `Block`. Users will need to manually use `with self.name_scope():` for children blocks and specify prefix for the top level block. Otherwise, it will lead to wrong name scopes and can return parameters of children blocks that are not in the current name scope. An example for initializing the Block and Parameter in Gluon 1.x:
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
Review comment:
```suggestion
- The dataset is not fully [supported by the backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
Review comment:
```suggestion
[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes a default value of None; when set to `True` the dataloader will compile the python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
Review comment:
```suggestion
In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and the deferred compute mechanism.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
Review comment:
```suggestion
To help users migrate smoothly to use these simplified interfaces, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
Review comment:
```suggestion
- **Imperative-only coding experience**: with the deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
+
+
+### NumPy-compatible Programming Experience
+#### NumPy Arrays
+MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that needs attention, as mentioned below.
Review comment:
```suggestion
MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use the NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that need attention, as mentioned below.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
+
+
+### NumPy-compatible Programming Experience
+#### NumPy Arrays
+MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that needs attention, as mentioned below.
+**Migration Guide**:
+
+1. Currently, NumPy ndarray only supports `default` storage type, other storage types, like `row_sparse`, `csr` are not supported. Also, `tostype()` attribute is deprecated.
+
+2. Users can use `as_np_ndarray` attribute to switch from a legacy NDArray to NumPy ndarray just like this:
+ ```{.python}
+ import mxnet as mx
+ nd_array = mx.ones((5,3))
+ np_array = nd_array.as_np_ndarray()
+ ```
+
+3. Compared with legacy NDArray, some attributes are deprecated in NumPy ndarray. Listed below are some of the deprecated APIs and their corresponding replacements in NumPy ndarray, others can be found in [**Appendix/NumPy Array Deprecated Attributes**](#NumPy-Array-Deprecated-Attributes).
+ | Deprecated Attributes | NumPy ndarray Equivalent |
+ | ----------------------------------------------------- | ------------------------------ |
+ | `a.asscalar()` | `a.item()` |
+ | `a.as_in_context()` | `a.as_in_ctx()` |
+ | `a.context` | `a.ctx` |
+ | `a.reshape_like(b)` | `a.reshape(b.shape)` |
+ | `a.zeros_like(b)` | `mx.np.zeros_like(b)` |
+ | `a.ones_like(b)` | `mx.np.ones_like(b)` |
+
+4. Compared with legacy NDArray, some attributes will have different behaviors and take different inputs.
+ | Attribute | Legacy Inputs | NumPy Inputs |
+ | ----------------------------- | ------------------------ | -------- |
+ | `a.reshape(*args, **kwargs)` | **shape**: Some dimensions of the shape can take special values from the set {0, -1, -2, -3, -4}. <br> The significance of each is explained below: <br> ``0`` copy this dimension from the input to the output shape. <br> ``-1`` infers the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy all/remainder of the input dimensions to the output shape. <br> ``-3`` use the product of two consecutive dimensions of the input shape as the output dimension. <br> ``-4`` split one dimension of the input into two dimensions passed subsequent to -4 in shape (can contain -1). <br> **reverse**: If set to 1, then the special values are inferred from right to left | **shape**: shape parameter will be **positional argument** rather than key-word argument. <br> Some dimensions of the shape can take special values from the set {-1, -2, -3, -4, -5, -6}. <br> The significance of each is explained below: <br> ``-1`` infers
the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy this dimension from the input to the output shape. <br> ``-3`` will skip current dimension if and only if the current dim size is one. <br> ``-4`` copy all remain of the input dimensions to the output shape. <br> ``-5`` use the product of two consecutive dimensions of the input shape as the output. <br> ``-6`` split one dimension of the input into two dimensions passed subsequent to -6 in the new shape. <br> **reverse**: No **reverse** parameter for `np.reshape` but for `npx.reshape`. <br> **order**: Read the elements of `a` using this index order, and place the elements into the reshaped array using this index order. |
Review comment:
```suggestion
| `a.reshape(*args, **kwargs)` | **shape**: Some dimensions of the shape can take special values from the set {0, -1, -2, -3, -4}. <br> The significance of each is explained below: <br> ``0`` copy this dimension from the input to the output shape. <br> ``-1`` infers the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy all/remainder of the input dimensions to the output shape. <br> ``-3`` use the product of two consecutive dimensions of the input shape as the output dimension. <br> ``-4`` split one dimension of the input into two dimensions passed subsequent to -4 in shape (can contain -1). <br> **reverse**: If set to 1, then the special values are inferred from right to left | **shape**: shape parameter will be **positional argument** rather than key-word argument. <br> Some dimensions of the shape can take special values from the set {-1, -2, -3, -4, -5, -6}. <br> The significance of each is explained below: <br> ``-1`` infer
s the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy this dimension from the input to the output shape. <br> ``-3`` skip the current dimension if and only if the current dim size is one. <br> ``-4`` copy all the remaining the input dimensions to the output shape. <br> ``-5`` use the product of two consecutive dimensions of the input shape as the output. <br> ``-6`` split one dimension of the input into two dimensions passed subsequent to -6 in the new shape. <br> **reverse**: No **reverse** parameter for `np.reshape` but for `npx.reshape`. <br> **order**: Read the elements of `a` using this index order, and place the elements into the reshaped array using this index order. |
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
Review comment:
```suggestion
- Bachify is not fully [supported by the backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
+
+
+### NumPy-compatible Programming Experience
+#### NumPy Arrays
+MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that needs attention, as mentioned below.
+**Migration Guide**:
+
+1. Currently, NumPy ndarray only supports `default` storage type, other storage types, like `row_sparse`, `csr` are not supported. Also, `tostype()` attribute is deprecated.
+
+2. Users can use `as_np_ndarray` attribute to switch from a legacy NDArray to NumPy ndarray just like this:
+ ```{.python}
+ import mxnet as mx
+ nd_array = mx.ones((5,3))
+ np_array = nd_array.as_np_ndarray()
+ ```
+
+3. Compared with legacy NDArray, some attributes are deprecated in NumPy ndarray. Listed below are some of the deprecated APIs and their corresponding replacements in NumPy ndarray, others can be found in [**Appendix/NumPy Array Deprecated Attributes**](#NumPy-Array-Deprecated-Attributes).
+ | Deprecated Attributes | NumPy ndarray Equivalent |
+ | ----------------------------------------------------- | ------------------------------ |
+ | `a.asscalar()` | `a.item()` |
+ | `a.as_in_context()` | `a.as_in_ctx()` |
+ | `a.context` | `a.ctx` |
+ | `a.reshape_like(b)` | `a.reshape(b.shape)` |
+ | `a.zeros_like(b)` | `mx.np.zeros_like(b)` |
+ | `a.ones_like(b)` | `mx.np.ones_like(b)` |
+
+4. Compared with legacy NDArray, some attributes will have different behaviors and take different inputs.
+ | Attribute | Legacy Inputs | NumPy Inputs |
+ | ----------------------------- | ------------------------ | -------- |
+ | `a.reshape(*args, **kwargs)` | **shape**: Some dimensions of the shape can take special values from the set {0, -1, -2, -3, -4}. <br> The significance of each is explained below: <br> ``0`` copy this dimension from the input to the output shape. <br> ``-1`` infers the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy all/remainder of the input dimensions to the output shape. <br> ``-3`` use the product of two consecutive dimensions of the input shape as the output dimension. <br> ``-4`` split one dimension of the input into two dimensions passed subsequent to -4 in shape (can contain -1). <br> **reverse**: If set to 1, then the special values are inferred from right to left | **shape**: shape parameter will be **positional argument** rather than key-word argument. <br> Some dimensions of the shape can take special values from the set {-1, -2, -3, -4, -5, -6}. <br> The significance of each is explained below: <br> ``-1`` infers
the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy this dimension from the input to the output shape. <br> ``-3`` will skip current dimension if and only if the current dim size is one. <br> ``-4`` copy all remain of the input dimensions to the output shape. <br> ``-5`` use the product of two consecutive dimensions of the input shape as the output. <br> ``-6`` split one dimension of the input into two dimensions passed subsequent to -6 in the new shape. <br> **reverse**: No **reverse** parameter for `np.reshape` but for `npx.reshape`. <br> **order**: Read the elements of `a` using this index order, and place the elements into the reshaped array using this index order. |
+
+
+#### NumPy and NumPy-extension Operators
+Most of the legacy NDArray operators(`mx.nd.op`) have the equivalent ones in np/npx namespace, users can just repalce them with `mx.np.op` or `mx.npx.op` to migrate. Some of the operators will have different inputs and behaviors as listed in the table below.
+**Migration Guide**:
+
+1. Operators migration with name/inputs changes
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.flatten(*args, **kwargs)` | `mx.npx.batch_flatten(*args, **kwargs)` | moved to `npx` namespace with new name `batch_flatten` |
+ | `mx.nd.concat(a, b, c)` | `mx.np.concatenate([a, b, c])` | - moved to `np` namespace with new name `concatenate`. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.stack(a, b, c)` | `mx.np.stack([a, b, c])` | - moved to `np` namespace. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.SliceChannel(*args, **kwargs)` | `mx.npx.slice_channel(*args, **kwargs)` | - moved to `npx` namespace with new name `slice_channel`. |
+ | `mx.nd.FullyConnected(*args, **kwargs)` | `mx.npx.fully_connected(*args, **kwargs)` | - moved to `npx` namespace with new name `fully_connected`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.elemwise_add(a, b)` | `a + b` | - Just use ndarray python operator. |
+ | `mx.nd.elemwise_mul(a, b)` | `mx.np.multiply(a, b)` | - Use `multiply` operator in `np` namespace. |
+
+2. Operators migration with multiple steps: `mx.nd.mean` -> `mx.np.mean`:
+```{.python}
+import mxnet as mx
+# Legacy: calculate mean value with reduction on axis 1
+# with `exclude` option on
+nd_mean = mx.nd.mean(data, axis=1, exclude=1)
+
+# Numpy: no exclude option to users, but user can perform steps as follow
+axes = list(range(data.ndim))
+del axes[1]
+np_mean = mx.np.mean(data, axis=axes)
+```
+
+3. Random Operators
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ---------------------------- |
+ | `mx.random.uniform(-1.0, 1.0, shape=(2, 3))` <br> `mx.nd.random.uniform(-1.0, 1.0, shape=(2, 3))` | `mx.np.random.uniform(-1.0, 1.0, size=(2, 3))` | For all the NumPy random operators, use **size** key word instead of **shape** |
+ | `mx.nd.random.multinomial(*args, **kwargs)` | `mx.npx.random.categorical(*args, **kwargs)` | [use `npx.random.categorical` to have the behavior of drawing 1 sample from multiple distributions.](https://github.com/apache/incubator-mxnet/issues/20373#issuecomment-869120214) |
+
+4. Control Flow Operators
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.contrib.foreach(body, data, init_states, name)` | `mx.npx.foreach(body, data, init_states, name)` | - moved to `npx` namespace. <br> - Will not support global variables as body's inputs(body's inputs must be either data or states or both) |
+ | `mx.nd.contrib.while_loop(cond, func, loop_vars, max_iterations, name)` | `mx.npx.while_loop(cond, func, loop_vars, max_iterations, name)` | - moved to `npx` namespace. <br> - Will not support global variables as cond or func's inputs(cond or func's inputs must be in loop_vars) |
+ | `mx.nd.contrib.cond(pred, then_func, else_func, inputs, name)` | `mx.npx.cond(pred, then_func, else_func, name)` | - moved to `npx` namespace. <br> - users needs to provide the inputs of pred, then_func and else_func as inputs <br> - Will not support global variables as pred, then_func or else_func's inputs(pred, then_func or else_func's inputs must be in inputs) |
+
+5. Functionalities
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.save(*args, **kwargs)` | `mx.npx.savez(*args, **kwargs)` | - moved to `npx` namespace. <br> - Only accept positional arguments, try to flatten the list/dict before feed in |
+ | `mx.nd.load(*args, **kwargs)` | `mx.npx.load(*args, **kwargs)` | - moved to `npx` namespace. |
+ | `mx.nd.waitall()` | `mx.npx.waitall()` | - moved to `npx` namespace. |
+
+Other operator changes are included in [**Appendix/NumPy and NumPy-extension Operators**](#NumPy-and-NumPy-extension-Operators1)
+
+
+
+### Layers and Blocks
+With deferred compute and tracing being introduced in Gluon2.0, users do not need to interact with symbols any more. There are a lot of changes in building a model with Gluon API, including parameter management and naming, forward pass computing and parameter shape inferencing. We will provide a step-by-step migration guidance on how to build a model with new APIs.
Review comment:
```suggestion
With the deferred compute and tracing being introduced in Gluon2.0, users do not need to interact with symbols any more. There are a lot of changes in building a model with Gluon API, including parameter management and naming, forward pass computing and parameter shape inferencing. We provide step-by-step migration guidance on how to build a model with new APIs.
```
##########
File path: docs/python_docs/python/tutorials/getting-started/gluon_migration_guide.md
##########
@@ -0,0 +1,453 @@
+<!--- Licensed to the Apache Software Foundation (ASF) under one -->
+<!--- or more contributor license agreements. See the NOTICE file -->
+<!--- distributed with this work for additional information -->
+<!--- regarding copyright ownership. The ASF licenses this file -->
+<!--- to you under the Apache License, Version 2.0 (the -->
+<!--- "License"); you may not use this file except in compliance -->
+<!--- with the License. You may obtain a copy of the License at -->
+
+<!--- http://www.apache.org/licenses/LICENSE-2.0 -->
+
+<!--- Unless required by applicable law or agreed to in writing, -->
+<!--- software distributed under the License is distributed on an -->
+<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->
+<!--- KIND, either express or implied. See the License for the -->
+<!--- specific language governing permissions and limitations -->
+<!--- under the License. -->
+
+
+# Gluon2.0: Migration Guide
+
+## Overview
+Since the introduction of the Gluon API in MXNet 1.x, it has superceded commonly used symbolic, module and model APIs for model development. In fact, Gluon was the first in deep learning community to unify the flexibility of imperative programming with the performance benefits of symbolic programming, through just-in-time compilation.
+
+In Gluon2.0, we extend the support to MXNet numpy and numpy extension with simplified interface and new functionalities:
+
+- **Simplified hybridization with deferred compute and tracing**: Deferred compute allows the imperative execution to be used for graph construction, which allows us to unify the historic divergence of NDArray and Symbol. Hybridization now works in a simplified hybrid forward interface. Users only need to specify the computation through imperative programming. Hybridization also works through tracing, i.e. tracing the data flow of the first input data to create graph.
+
+- **Data 2.0**: The new design for data loading in Gluon allows hybridizing and deploying data processing pipeline in the same way as model hybridization. The new C++ data loader improves data loading efficiency on CIFAR 10 by 50%.
+
+- **Distributed 2.0**: The new distributed-training design in Gluon 2.0 provides a unified distributed data parallel interface across native Parameter Server, BytePS, and Horovod, and is extensible for supporting custom distributed training libraries.
+
+- **Gluon Probability**: parameterizable probability distributions and sampling functions to facilitate more areas of research such as Baysian methods and AutoML.
+
+- **Gluon Metrics** and **Optimizers**: refactored with MXNet numpy interface and addressed legacy issues.
+
+Adopting these new functionalities may or may not require modifications on your models. But don't worry, this migration guide will go through a high-level mapping from old functionality to new APIs and make Gluon2.0 migration a hassle-free experience.
+
+## Data Pipeline
+**What's new**: In Gluon2.0, `MultithreadingDataLoader` is introduced to speed up the data loading pipeline. It will use the pure MXNet C++ implementation of dataloader, datasets and batchify functions. So, you can use either MXNet internal multithreading mode dataloader or python multiprocessing mode dataloader in Gluon2.0.
+
+**Migration Guide**: Users can continue with the traditional gluon.data.Dataloader and the C++ backend will be applied automatically.
+
+[Gluon2.0 dataloader](../../api/gluon/data/index.rst#mxnet.gluon.data.DataLoader) will provide a new parameter called `try_nopython`. This parameter takes default value of None; when set to `True` the dataloader will compile python dataloading pipeline into pure MXNet c++ implementation. The compilation is not guaranteed to support all use cases, but it will fallback to python in case of failure:
+
+- The dataset is not fully [supported by backend](../../api/gluon/data/index.rst#mxnet.gluon.data.Dataset)(e.g., there are custom python datasets).
+
+- Transform is not fully hybridizable.
+
+- Bachify is not fully [supported by backend](https://github.com/apache/incubator-mxnet/blob/master/python/mxnet/gluon/data/batchify.py).
+
+
+You can refer to [Step5 in Crash Course](https://mxnet.apache.org/versions/master/api/python/docs/tutorials/getting-started/crash-course/5-datasets.html#New-in-MXNet-2.0:-faster-C++-backend-dataloaders) for a detailed performance increase with C++ backend.
+## Modeling
+In Gluon2.0, users will have a brand new modeling experience with NumPy-compatible APIs and deferred compute mechanism.
+
+- **NumPy-compatible programing experience**: users can build their models with MXNet implementation with NumPy array library, NumPy-compatible math operators and some neural network extension operators.
+
+- **Imperative-only coding experience**: with deferred compute and tracing being introduced, users only need to specify the computation through imperative coding but can still make hybridization work. Users will no longer need to interact with symbol APIs.
+
+To help users migrate smoothly to use these simplified interface, we will provide the following guidance on how to replace legacy operators with NumPy-compatible operators, how to build models with `forward` instead of `hybrid_forward` and how to use `Parameter` class to register your parameters.
+
+
+### NumPy-compatible Programming Experience
+#### NumPy Arrays
+MXNet [NumPy ndarray(i.e. `mx.np.ndarray`)](../../api/np/arrays.ndarray.html) is a multidimensional container of items of the same type and size. Most of its properties and attributes are the same as legacy NDArrays(i.e. `mx.nd.ndarray`), so users can use NumPy array library just as they did with legacy NDArrays. But, there are still some changes and deprecations that needs attention, as mentioned below.
+**Migration Guide**:
+
+1. Currently, NumPy ndarray only supports `default` storage type, other storage types, like `row_sparse`, `csr` are not supported. Also, `tostype()` attribute is deprecated.
+
+2. Users can use `as_np_ndarray` attribute to switch from a legacy NDArray to NumPy ndarray just like this:
+ ```{.python}
+ import mxnet as mx
+ nd_array = mx.ones((5,3))
+ np_array = nd_array.as_np_ndarray()
+ ```
+
+3. Compared with legacy NDArray, some attributes are deprecated in NumPy ndarray. Listed below are some of the deprecated APIs and their corresponding replacements in NumPy ndarray, others can be found in [**Appendix/NumPy Array Deprecated Attributes**](#NumPy-Array-Deprecated-Attributes).
+ | Deprecated Attributes | NumPy ndarray Equivalent |
+ | ----------------------------------------------------- | ------------------------------ |
+ | `a.asscalar()` | `a.item()` |
+ | `a.as_in_context()` | `a.as_in_ctx()` |
+ | `a.context` | `a.ctx` |
+ | `a.reshape_like(b)` | `a.reshape(b.shape)` |
+ | `a.zeros_like(b)` | `mx.np.zeros_like(b)` |
+ | `a.ones_like(b)` | `mx.np.ones_like(b)` |
+
+4. Compared with legacy NDArray, some attributes will have different behaviors and take different inputs.
+ | Attribute | Legacy Inputs | NumPy Inputs |
+ | ----------------------------- | ------------------------ | -------- |
+ | `a.reshape(*args, **kwargs)` | **shape**: Some dimensions of the shape can take special values from the set {0, -1, -2, -3, -4}. <br> The significance of each is explained below: <br> ``0`` copy this dimension from the input to the output shape. <br> ``-1`` infers the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy all/remainder of the input dimensions to the output shape. <br> ``-3`` use the product of two consecutive dimensions of the input shape as the output dimension. <br> ``-4`` split one dimension of the input into two dimensions passed subsequent to -4 in shape (can contain -1). <br> **reverse**: If set to 1, then the special values are inferred from right to left | **shape**: shape parameter will be **positional argument** rather than key-word argument. <br> Some dimensions of the shape can take special values from the set {-1, -2, -3, -4, -5, -6}. <br> The significance of each is explained below: <br> ``-1`` infers
the dimension of the output shape by using the remainder of the input dimensions. <br> ``-2`` copy this dimension from the input to the output shape. <br> ``-3`` will skip current dimension if and only if the current dim size is one. <br> ``-4`` copy all remain of the input dimensions to the output shape. <br> ``-5`` use the product of two consecutive dimensions of the input shape as the output. <br> ``-6`` split one dimension of the input into two dimensions passed subsequent to -6 in the new shape. <br> **reverse**: No **reverse** parameter for `np.reshape` but for `npx.reshape`. <br> **order**: Read the elements of `a` using this index order, and place the elements into the reshaped array using this index order. |
+
+
+#### NumPy and NumPy-extension Operators
+Most of the legacy NDArray operators(`mx.nd.op`) have the equivalent ones in np/npx namespace, users can just repalce them with `mx.np.op` or `mx.npx.op` to migrate. Some of the operators will have different inputs and behaviors as listed in the table below.
+**Migration Guide**:
+
+1. Operators migration with name/inputs changes
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.flatten(*args, **kwargs)` | `mx.npx.batch_flatten(*args, **kwargs)` | moved to `npx` namespace with new name `batch_flatten` |
+ | `mx.nd.concat(a, b, c)` | `mx.np.concatenate([a, b, c])` | - moved to `np` namespace with new name `concatenate`. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.stack(a, b, c)` | `mx.np.stack([a, b, c])` | - moved to `np` namespace. <br> - use list of ndarrays as input rather than positional ndarrays |
+ | `mx.nd.SliceChannel(*args, **kwargs)` | `mx.npx.slice_channel(*args, **kwargs)` | - moved to `npx` namespace with new name `slice_channel`. |
+ | `mx.nd.FullyConnected(*args, **kwargs)` | `mx.npx.fully_connected(*args, **kwargs)` | - moved to `npx` namespace with new name `fully_connected`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.Activation(*args, **kwargs)` | `mx.npx.activation(*args, **kwargs)` | - moved to `npx` namespace with new name `activation`. |
+ | `mx.nd.elemwise_add(a, b)` | `a + b` | - Just use ndarray python operator. |
+ | `mx.nd.elemwise_mul(a, b)` | `mx.np.multiply(a, b)` | - Use `multiply` operator in `np` namespace. |
+
+2. Operators migration with multiple steps: `mx.nd.mean` -> `mx.np.mean`:
+```{.python}
+import mxnet as mx
+# Legacy: calculate mean value with reduction on axis 1
+# with `exclude` option on
+nd_mean = mx.nd.mean(data, axis=1, exclude=1)
+
+# Numpy: no exclude option to users, but user can perform steps as follow
+axes = list(range(data.ndim))
+del axes[1]
+np_mean = mx.np.mean(data, axis=axes)
+```
+
+3. Random Operators
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ---------------------------- |
+ | `mx.random.uniform(-1.0, 1.0, shape=(2, 3))` <br> `mx.nd.random.uniform(-1.0, 1.0, shape=(2, 3))` | `mx.np.random.uniform(-1.0, 1.0, size=(2, 3))` | For all the NumPy random operators, use **size** key word instead of **shape** |
+ | `mx.nd.random.multinomial(*args, **kwargs)` | `mx.npx.random.categorical(*args, **kwargs)` | [use `npx.random.categorical` to have the behavior of drawing 1 sample from multiple distributions.](https://github.com/apache/incubator-mxnet/issues/20373#issuecomment-869120214) |
+
+4. Control Flow Operators
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.contrib.foreach(body, data, init_states, name)` | `mx.npx.foreach(body, data, init_states, name)` | - moved to `npx` namespace. <br> - Will not support global variables as body's inputs(body's inputs must be either data or states or both) |
+ | `mx.nd.contrib.while_loop(cond, func, loop_vars, max_iterations, name)` | `mx.npx.while_loop(cond, func, loop_vars, max_iterations, name)` | - moved to `npx` namespace. <br> - Will not support global variables as cond or func's inputs(cond or func's inputs must be in loop_vars) |
+ | `mx.nd.contrib.cond(pred, then_func, else_func, inputs, name)` | `mx.npx.cond(pred, then_func, else_func, name)` | - moved to `npx` namespace. <br> - users needs to provide the inputs of pred, then_func and else_func as inputs <br> - Will not support global variables as pred, then_func or else_func's inputs(pred, then_func or else_func's inputs must be in inputs) |
+
+5. Functionalities
+ | Legacy Operators | NumPy Operators Equivalent | Changes |
+ | ----------------------------------------------------- | ------------------------------ | ------------------- |
+ | `mx.nd.save(*args, **kwargs)` | `mx.npx.savez(*args, **kwargs)` | - moved to `npx` namespace. <br> - Only accept positional arguments, try to flatten the list/dict before feed in |
+ | `mx.nd.load(*args, **kwargs)` | `mx.npx.load(*args, **kwargs)` | - moved to `npx` namespace. |
+ | `mx.nd.waitall()` | `mx.npx.waitall()` | - moved to `npx` namespace. |
+
+Other operator changes are included in [**Appendix/NumPy and NumPy-extension Operators**](#NumPy-and-NumPy-extension-Operators1)
+
+
+
+### Layers and Blocks
+With deferred compute and tracing being introduced in Gluon2.0, users do not need to interact with symbols any more. There are a lot of changes in building a model with Gluon API, including parameter management and naming, forward pass computing and parameter shape inferencing. We will provide a step-by-step migration guidance on how to build a model with new APIs.
+
+#### Parameter Management and Block Naming
+In Gluon, each Parameter or Block has a name (and prefix). Parameter names are specified by users and Block names can be either specified by users or automatically created. In Gluon 1.x, parameters are accessed via the `params` variable of the `ParameterDict` in `Block`. Users will need to manually use `with self.name_scope():` for children blocks and specify prefix for the top level block. Otherwise, it will lead to wrong name scopes and can return parameters of children blocks that are not in current name scope. An example for initializing the Block and Parameter in Gluon 1.x:
+```{.python}
+from mxnet.gluon import Parameter, Constant, HybridBlock
+class SampleBlock(HybridBlock):
+ def __init__(self):
+ super(SampleBlock, self).__init__()
+ with self.name_scope():
+ # Access parameters, which are iterated during training
+ self.weight = self.params.get('weight')
+ # Access constant parameters, which are not iterated during training
+ self.weight = self.params.get_constant('const', const_arr)
+```
+Now in Gluon 2.0, Block/HybridBlock objects will not maintain the parameter dictionary(`ParameterDict`). Instead, users can access these parameters via `Parameter` class and `Constant` class. These parameters will be registered automatically as part of the Block. Users will no longer need to manage the name scope for children blocks and hence can remove `with self.name_scope():` this statement. For example:
+```{.python}
+class SampleBlock(HybridBlock):
+ def __init__(self):
+ super(SampleBlock, self).__init__()
+ # Access parameters, which are iterated during training
+ self.weight = Parameter('weight')
+ # Access constant parameters, which are not iterated during training
+ self.weight = Constant('const', const_arr)
+```
+Also, there will be new mechanism for parameter loading, sharing and setting context.
Review comment:
```suggestion
Also, there will be new mechanisms for parameter loading, sharing and setting context.
```
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