Files
pytorch/test/cpp/jit/test_backend_lib.cpp
Martin Yuan b2520ab3dc Add a demo backend with compiler (#52603)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52603

This PR introduced a backend with minimum compilation capability to the to_<backend> flow. The targets are:

- Demonstrate the end-to-end flow with adding a backend -> compilation -> runtime
- How the backend compilation errors be surfaced to the user, with the original model's source code information. (C++ only in this PR. Python APIs will be demonstrated in a following PR.)

Changes:

- Compilation

1. A backend with minimum compilation features, "backend_with_compiler_demo" is added.
2. The compilation happens AOT in the ```pre_process``` function registered to this backend.
3. Compiled results are stored in a string blob for each method. They are serialized to the lowered module with ```__get_state__``` function.
4. Error message with model source code is thrown, for features not handled by the backend compiler.

- Runtime

1. The compiled blob is loaded in ```__set_state__``` method.
2. The ```compile``` function of the backend pass through the AOT compiled blob. (TODO: parsing the blob to the format that the backend can understand can happen here.)
3. The ```execute``` function of the backend executes the specified method (handle).

Test Plan:
- ```BackendTest.TestCompiler```: the C++ end-to-end demonstration on a supported model. After compilation and running, the lowered model produces the same result as the original torchscript model.
- ```BackendTest.TestCompilerNotSupport```: Demonstrate the error message from the AOT compilation for a feature not supported from the input module. The error message looks like:

```
"The node of aten::mul is not supported in this compiler. Source code:   File "<string>", line 3

    def forward(self, x, h):
        return x * h
               ~~~~~ <--- HERE
```

Reviewed By: raziel

Differential Revision: D26593968

Pulled By: iseeyuan

fbshipit-source-id: 8f264f60a0470e9f07e36fdeccbf17da6c1d7cd7
2021-02-26 11:53:34 -08:00

76 lines
2.3 KiB
C++

#include <torch/csrc/jit/backends/backend.h>
namespace torch {
namespace jit {
// This test JIT backend is intended to do the minimal amount of work
// necessary to test that the JIT backend registration endpoints and
// code generation are working correctly. It is not intended to
// produce numerically correct results.
class TestBackend : public PyTorchBackendInterface {
public:
// Constructor.
explicit TestBackend() {}
virtual ~TestBackend() = default;
c10::impl::GenericDict compile(
c10::IValue processed,
c10::impl::GenericDict method_compile_spec) override {
auto spec =
c10::impl::toTypedDict<std::string, at::IValue>(method_compile_spec);
// Return the same string as a value for every key in method_compile_spec.
auto handles = c10::Dict<std::string, std::string>();
for (const auto& it : spec) {
handles.insert(it.key(), it.key());
}
return c10::impl::toGenericDict(handles);
}
c10::impl::GenericList execute(
c10::IValue handle,
c10::impl::GenericList inputs) override {
TORCH_INTERNAL_ASSERT(handle.isString());
TORCH_INTERNAL_ASSERT(inputs.size() > 0);
c10::List<at::Tensor> output_list;
// Implement simple accumulator and negative accumulator (?) ops. Return one
// or both of them depending on the handle to make sure multiple outputs are
// handled.
c10::IValue value = inputs[0];
at::Tensor accum = value.toTensor();
accum = accum.clone();
at::Tensor sub_accum = value.toTensor();
sub_accum = sub_accum.clone();
for (size_t i = 1, e = inputs.size(); i < e; ++i) {
value = inputs[i];
accum.add_(value.toTensor(), 1.0);
sub_accum.sub_(value.toTensor(), 1.0);
}
if (handle.toStringRef() == "accum") {
output_list.emplace_back(accum);
} else if (handle.toStringRef() == "sub_accum") {
output_list.emplace_back(sub_accum);
} else if (handle.toStringRef() == "forward") {
output_list.emplace_back(accum);
output_list.emplace_back(sub_accum);
}
return c10::impl::toList(output_list);
}
};
namespace {
c10::IValue preprocess(
const Module& mod,
const c10::Dict<IValue, IValue>& method_compile_spec) {
return mod._ivalue();
}
static auto cls = torch::jit::backend<TestBackend>("test_backend", preprocess);
} // namespace
} // namespace jit
} // namespace torch