[GitHub] anirudh2290 commented on a change in pull request #11025: added ravel/unravel operators

[GitBox <gi...@apache.org>]

anirudh2290 commented on a change in pull request #11025: added ravel/unravel operators
URL: https://github.com/apache/incubator-mxnet/pull/11025#discussion_r190333867
 
 

 ##########
 File path: src/operator/tensor/ravel.h
 ##########
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+/*
+ * 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.
+ */
+
+/*!
+ * Copyright (c) 2018 by Contributors
+ * \file ravel.h
+ * \brief Operators for ravel/unravel indices.
+ */
+#ifndef MXNET_OPERATOR_TENSOR_RAVEL_H_
+#define MXNET_OPERATOR_TENSOR_RAVEL_H_
+
+#include <mxnet/operator_util.h>
+#include <vector>
+#include <algorithm>
+#include "../mshadow_op.h"
+#include "../mxnet_op.h"
+#include "../operator_common.h"
+#include "../elemwise_op_common.h"
+
+namespace mxnet {
+namespace op {
+
+struct RavelParam : public dmlc::Parameter<RavelParam> {
+  TShape shape;
+  DMLC_DECLARE_PARAMETER(RavelParam) {
+    DMLC_DECLARE_FIELD(shape)
+      .set_default(TShape())
+      .describe("Shape of the array into which the multi-indices apply.");
+  }
+};
+
+inline bool RavelOpShape(const nnvm::NodeAttrs& attrs,
+                         std::vector<TShape>* in_attrs,
+                         std::vector<TShape>* out_attrs) {
+  using namespace mshadow;
+  const TShape& shape = nnvm::get<RavelParam>(attrs.parsed).shape;
+  CHECK_EQ(in_attrs->size(), 1);
+  CHECK_EQ(out_attrs->size(), 1);
+  CHECK_GT(shape.ndim(), 0) << "Invalid shape parameter for ravel operator.";
+  if ((*in_attrs)[0].ndim() > 0) {
+    CHECK_EQ((*in_attrs)[0].ndim(), 2)
+      << "Input to ravel operator must be two-dimensional.";
+    CHECK_EQ((*in_attrs)[0][0], shape.ndim())
+      << "First dimension of input of ravel operator does not match shape parameter dimension.";
+    SHAPE_ASSIGN_CHECK(*out_attrs, 0, Shape1((*in_attrs)[0][1]));
+    return true;
+  }
+  if ((*out_attrs)[0].ndim() > 0) {
+    SHAPE_ASSIGN_CHECK(*in_attrs, 0, Shape2(shape.ndim(), (*out_attrs)[0][0]));
+    return true;
+  }
+  return false;
+}
+
+inline bool UnravelOpShape(const nnvm::NodeAttrs& attrs,
+                           std::vector<TShape>* in_attrs,
+                           std::vector<TShape>* out_attrs) {
+  using namespace mshadow;
+  const TShape& shape = nnvm::get<RavelParam>(attrs.parsed).shape;
+  CHECK_EQ(in_attrs->size(), 1);
+  CHECK_EQ(out_attrs->size(), 1);
+  CHECK_GT(shape.ndim(), 0) << "Invalid shape parameter for unravel operator.";
+  if ((*in_attrs)[0].ndim() > 0) {
+    SHAPE_ASSIGN_CHECK(*out_attrs, 0, Shape2(shape.ndim(), (*in_attrs)[0][0]));
+    return true;
+  }
+  if ((*out_attrs)[0].ndim() > 0) {
+    CHECK_EQ((*out_attrs)[0].ndim(), 2)
+      << "Output of unravel operator must be two-dimensional.";
+    CHECK_EQ((*out_attrs)[0][0], shape.ndim())
+      << "First dimension of output of ravel operator does not match shape parameter dimension.";
+    SHAPE_ASSIGN_CHECK(*in_attrs, 0, Shape1((*out_attrs)[0][1]));
+    return true;
+  }
+  return false;
+}
+
+struct ravel_index {
+  template<typename DType>
+  MSHADOW_XINLINE static void Map(int i, index_t N, index_t ndim, index_t *shape,
+                                  DType *unravelled, DType *ravelled) {
+    index_t ret = 0;
+    #pragma unroll
+    for (index_t j = 0; j < ndim; ++j) {
+      ret = ret * shape[j] + unravelled[i+j*N];
+    }
+    ravelled[i] = ret;
+  }
+};
+
+struct unravel_index {
+  template<typename DType>
+  MSHADOW_XINLINE static void Map(int i, index_t N, index_t ndim, index_t *shape,
+                                  DType *unravelled, DType *ravelled) {
+    index_t idx(ravelled[i]);
+    #pragma unroll
+    for (int j = ndim; j--; ) {
 
 Review comment:
   I find this style a little confusing and would prefer `for(int j = ndim; j >= 0; j--)` . What is the motivation ?

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