Without this flag, when compiling with nvcc, if the compute architecture of a card does
not exactly match any of those listed for `-gencode arch=compute_<arch>,code=sm_<arch>`,
then the kernel will fail to run with:
```
cudaErrorNoKernelImageForDevice: no kernel image is available for execution on the device.
```
This can happen, for example, when compiling with an older cuda version
that does not support a newer architecture (e.g. T4 is `sm_75`, but cuda
9.2 only supports up to `sm_70`).
With the `-arch=<arch>` flag, the code will compile and run at the
supplied architecture.
- Unify test/CMakeLists.txt and unsupported/test/CMakeLists.txt
- Added `EIGEN_CUDA_FLAGS` that are appended to the set of flags passed
to the cuda compiler (nvcc or clang).
The latter is to support passing custom flags (e.g. `-arch=` to nvcc,
or to disable cuda-specific warnings).
This introduces new functions:
```
// returns kernel(args...) running on the CPU.
Eigen::run_on_cpu(Kernel kernel, Args&&... args);
// returns kernel(args...) running on the GPU.
Eigen::run_on_gpu(Kernel kernel, Args&&... args);
Eigen::run_on_gpu_with_hint(size_t buffer_capacity_hint, Kernel kernel, Args&&... args);
// returns kernel(args...) running on the GPU if using
// a GPU compiler, or CPU otherwise.
Eigen::run(Kernel kernel, Args&&... args);
Eigen::run_with_hint(size_t buffer_capacity_hint, Kernel kernel, Args&&... args);
```
Running on the GPU is accomplished by:
- Serializing the kernel inputs on the CPU
- Transferring the inputs to the GPU
- Passing the kernel and serialized inputs to a GPU kernel
- Deserializing the inputs on the GPU
- Running `kernel(inputs...)` on the GPU
- Serializing all output parameters and the return value
- Transferring the serialized outputs back to the CPU
- Deserializing the outputs and return value on the CPU
- Returning the deserialized return value
All inputs must be serializable (currently POD types, `Eigen::Matrix`
and `Eigen::Array`). The kernel must also be POD (though usually
contains no actual data).
Tested on CUDA 9.1, 10.2, 11.3, with g++-6, g++-8, g++-10 respectively.
This MR depends on !622, !623, !624.
An analogue of `std::tuple` that works on device.
Context: I've tried `std::tuple` in various versions of NVCC and clang,
and although code seems to compile, it often fails to run - generating
"illegal memory access" errors, or "illegal instruction" errors.
This replacement does work on device.
The `Serializer<T>` class implements a binary serialization that
can write to (`serialize`) and read from (`deserialize`) a byte
buffer. Also added convenience routines for serializing
a list of arguments.
This will mainly be for testing, specifically to transfer data to
and from the GPU.
Removed all configurations that explicitly test or set the c++ standard
flags. The only place the standard is now configured is at the top of
the main `CMakeLists.txt` file, which can easily be updated (e.g. if
we decide to move to c++14+). This can also be set via command-line using
```
> cmake -DCMAKE_CXX_STANDARD 14
```
Kept the `EIGEN_TEST_CXX11` flag for now - that still controls whether to
build/run the `cxx11_*` tests. We will likely end up renaming these
tests and removing the `CXX11` subfolder.
Manually constructing an unaligned object declared as aligned
invokes UB, so we cannot technically check for alignment from
within the constructor. Newer versions of clang optimize away
this check.
Removing the affected tests.
