[GitHub] [tvm-rfcs] zxybazh commented on a change in pull request #28: Command Line Composition from Internal Registry

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

zxybazh commented on a change in pull request #28:
URL: https://github.com/apache/tvm-rfcs/pull/28#discussion_r722747074



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File path: rfcs/0028-command-line-registry-composition.md
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+- Feature Name: Command Line Composition from Internal Registry
+- Start Date: 2021-08-24
+- RFC PR: [apache/tvm-rfcs#28](https://github.com/apache/tvm-rfcs/pull/28)
+- GitHub Issue: [apache/tvm#0000](https://github.com/apache/tvm/issues/0000)
+
+# Summary
+[summary]: #summary
+
+Introducing a standardised form for `tvmc` arguments to be populated from internal registries in TVM.
+
+# Motivation
+[motivation]: #motivation
+
+Currently, when a user uses `tvmc`, they present a target string:
+```
+tvmc --target="woofles -mcpu=woof, c -mattr=+mwoof"
+```
+
+Using a target string here means that the entire `--target` argument is used as an opaque pass-through to the internal `Target` string parser. Users coming to TVM should be able to compose these options and get meaningful help when doing that composition with `tvmc`. As an example, using the default `argparse` behaviour, the arguments can be registered as follows:
+```python
+import argparse
+parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+parser.add_argument('--target', type=str, help='comma separated target list or target string')
+
+target_c = parser.add_argument_group('target c')
+target_c.add_argument('--target-c-mcpu', type=str, help='target c mcpu string')
+target_c.add_argument('--target-c-mattr', type=str, help='target c mattr string')
+
+target_llvm = parser.add_argument_group('target llvm')
+target_llvm.add_argument('--target-llvm-mcpu', type=str, help='target llvm mcpu string')
+target_llvm.add_argument('--target-llvm-mattr', type=str, help='target lvm mattr string')
+
+args = parser.parse_args()
+print(args)
+```
+
+The user can get help for all available target options:
+```
+usage: test.py [-h] [--target TARGET] [--target-c-mcpu TARGET_C_MCPU] [--target-c-mattr TARGET_C_MATTR] [--target-llvm-mcpu TARGET_LLVM_MCPU] [--target-llvm-mattr TARGET_LLVM_MATTR]
+
+optional arguments:
+  -h, --help            show this help message and exit
+  --target TARGET       comma separated target list or target string (default: None)
+
+target c:
+  --target-c-mcpu TARGET_C_MCPU
+                        target c mcpu string (default: None)
+  --target-c-mattr TARGET_C_MATTR
+                        target c mattr string (default: None)
+
+target llvm:
+  --target-llvm-mcpu TARGET_LLVM_MCPU
+                        target llvm mcpu string (default: None)
+  --target-llvm-mattr TARGET_LLVM_MATTR
+                        target lvm mattr string (default: None)
+```
+
+These are arranged in per-`Target` groups to allow the user to easily follow which are applicable and which aren't. The use can now replace their existing `Target` string, by using the documented `Target` options, with:
+```
+tvmc --target=woofles,c \
+    --target-woofles-mcpu=woof \
+    --target-c-mattr=+mwoof
+```
+
+# Guide-level explanation
+[guide-level-explanation]: #guide-level-explanation
+
+Alongside support for a target string, `tvmc` would populate a series of other arguments specific to targets which match the attributes found in the TargetKindRegistry in `target_kind.cc`. For example, consider a subset of the `c` `Target`:
+
+```
+TVM_REGISTER_TARGET_KIND("c", kDLCPU)
+    .add_attr_option<String>("mcpu")
+```
+
+This would be translated at the `tvmc` level to:
+```bash
+tvmc --target=c \
+    --target-c-mcpu=cortex-m3
+```
+
+Which would then allow the user to compose together these options, such as:
+
+```bash
+tvmc --target=cmsisnn,c \ # Specifying multiple targets to enable in priority order
+    --target-cmsisnn-mattr=+dsp \
+    --target-c-mcpu=cortex-m3
+```
+
+# Reference-level explanation
+[reference-level-explanation]: #reference-level-explanation
+
+There already exists a mechanism which provides Python with `PassConfig` information, via:
+
+```c++
+// Function Registry
+TVM_REGISTER_GLOBAL("transform.ListConfigs").set_body_typed(PassContext::ListConfigs);
+// Actual call
+Map<String, Map<String, String>> PassContext::ListConfigs() {
+  return PassConfigManager::Global()->ListConfigs();
+}
+// Implementation
+Map<String, Map<String, String>> ListConfigs() {
+    Map<String, Map<String, String>> configs;
+    for (const auto& kv : key2vtype_) {
+        Map<String, String> metadata;
+        metadata.Set("type", kv.second.type_key);
+        configs.Set(kv.first, metadata);
+    }
+    return configs;
+}
+```
+
+This can be replicated to provide the same information for `TargetKind` or any other registry and provide this information to generate arguments in `tvmc` using `argparse`:
+```
+parser.add_argument(f"--target-{kind}-{attr}", ...)
+```
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+# Rationale and alternatives
+[rationale-and-alternatives]: #rationale-and-alternatives
+
+There's a number of alternative methods for injecting this information which have been used in other CLIs but obfuscate some of the information from the CLI arguments themselves:
+- Continue using target strings
+- Specify JSON
+
+# Prior art
+[prior-art]: #prior-art
+
+This is not dissimilar to how `gcc` or `clang` provide options, [for example in gcc](https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html):
+```
+gcc -fsanitize=address -fsanitize-address-use-after-scope
+```
+
+# Unresolved questions
+[unresolved-questions]: #unresolved-questions
+

Review comment:
       Hi, just want to mention that `load_config_dict` is a function we use to parse target json strings in both python & c++ side using python json library. It is currently designed for single target though. I think it would take some effort, while feasible, to make modifications to work with heterogenes targets if we want to make the change.




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