pytorch/c10/core/impl/DeviceGuardImplInterface.cpp
Sherlock Huang a956c4ab1c Return NoOpDeviceGuardImpl in replace of CudaDeviceGuard when device is not available, or cpu-only build (#160532)
Summary:

To support exporting a cuda model on a CPU-only machine under fake tensor mode.
User commonly need to move sample inputs to the cuda device with .to("cuda:0") or .to("cuda") call.
This diff supports this.
I expect the following pattern to work
```
with FakeTensorMode(allow_non_fake_inputs=True):
    cuda_module = module.to("cuda:0")
    cuda_sample_inputs = tuple([x.to("cuda:0") for x in sample_inputs])
    with torch.no_grad():
        ep = torch.export.export(cuda_module, cuda_sample_inputs)
```

Test Plan:
CI

Rollback Plan:

Differential Revision: D80181887

Pull Request resolved: https://github.com/pytorch/pytorch/pull/160532
Approved by: https://github.com/henryoier, https://github.com/ezyang
2025-09-13 01:50:51 +00:00

42 lines
1.3 KiB
C++

#include <c10/core/impl/DeviceGuardImplInterface.h>
#include <c10/core/impl/FakeGuardImpl.h>
#include <array>
namespace c10::impl {
std::array<
std::atomic<const DeviceGuardImplInterface*>,
static_cast<size_t>(DeviceType::COMPILE_TIME_MAX_DEVICE_TYPES)>
device_guard_impl_registry;
DeviceGuardImplRegistrar::DeviceGuardImplRegistrar(
DeviceType type,
const DeviceGuardImplInterface* impl) {
device_guard_impl_registry[static_cast<size_t>(type)].store(impl);
}
namespace {
thread_local std::unique_ptr<DeviceGuardImplInterface> tls_fake_device_guard =
nullptr;
}
void ensureCUDADeviceGuardSet() {
constexpr auto cuda_idx = static_cast<std::size_t>(DeviceType::CUDA);
const DeviceGuardImplInterface* p =
device_guard_impl_registry[cuda_idx].load();
// A non-null `ptr` indicates that CUDA is already available.
if (p == nullptr || (p && p->deviceCount() == 0)) {
// In following cases, we override CUDA guard interface with a no-op
// device guard.
// 1. p == nullptr; Trying to get a cuda device guard on a cpu-only build.
// 2. p->deviceCount() == 0; cuda build enabled, but no cuda devices
// available.
tls_fake_device_guard = std::make_unique<FakeGuardImpl<DeviceType::CUDA>>();
device_guard_impl_registry[cuda_idx].store(tls_fake_device_guard.get());
}
}
} // namespace c10::impl