Wrap workaround for cpp custom types a bit prettier and add an example

[dzhulgakov]

Summary: As a temporary demonstration on how to extend this hack further until custom C types are ready.

Differential Revision: D14742020

[ezyang]

This broke master:

Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp: In function 'at::Tensor at::native::fbgemm_pack_quantized_matrix(const at::Tensor&, int64_t, int64_t)':
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:244:19: error: 'make_unique' is not a member of 'std'
Apr 04 02:40:54    auto ptr = std::make_unique<fbgemm::PackBMatrix<int8_t>>(
Apr 04 02:40:54                    ^~~~~~~~~~~
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:244:19: note: suggested alternative: '__unique'
Apr 04 02:40:54    auto ptr = std::make_unique<fbgemm::PackBMatrix<int8_t>>(
Apr 04 02:40:54                    ^~~~~~~~~~~
Apr 04 02:40:54                    __unique
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:244:57: error: expected primary-expression before '>' token
Apr 04 02:40:54    auto ptr = std::make_unique<fbgemm::PackBMatrix<int8_t>>(
Apr 04 02:40:54                                                          ^~
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:246:16: error: left operand of comma operator has no effect [-Werror=unused-value]
Apr 04 02:40:54        /*nRow=*/K,
Apr 04 02:40:54                 ^
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:247:16: error: right operand of comma operator has no effect [-Werror=unused-value]
Apr 04 02:40:54        /*nCol=*/N,
Apr 04 02:40:54                 ^
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:248:16: error: right operand of comma operator has no effect [-Werror=unused-value]
Apr 04 02:40:54        /*smat=*/contiguous_ptr,
Apr 04 02:40:54                 ^~~~~~~~~~~~~~
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:249:14: error: right operand of comma operator has no effect [-Werror=unused-value]
Apr 04 02:40:54        /*ld=*/K,
Apr 04 02:40:54               ^
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:250:16: error: right operand of comma operator has no effect [-Werror=unused-value]
Apr 04 02:40:54        /*pmat=*/nullptr, // PackBMatrix manages ownership of pmat
Apr 04 02:40:54                 ^~~~~~~
Apr 04 02:40:54 /var/lib/jenkins/workspace/aten/src/ATen/native/QuantizedLinear.cpp:251:18: error: right operand of comma operator has no effect [-Werror=unused-value]
Apr 04 02:40:54        /*groups=*/1);
Apr 04 02:40:54                   ^
Apr 04 02:40:54 cc1plus: all warnings being treated as errors
Apr 04 02:40:54 caffe2/CMakeFiles/caffe2.dir/build.make:2625: recipe for target 'caffe2/CMakeFiles/caffe2.dir/__/aten/src/ATen/native/QuantizedLinear.cpp.o' failed
Apr 04 02:40:54 make[2]: *** [caffe2/CMakeFiles/caffe2.dir/__/aten/src/ATen/native/QuantizedLinear.cpp.o] Error 1
Apr 04 02:40:54 make[2]: *** Waiting for unfinished jobs....
Apr 04 02:40:54 make[1]: *** [caffe2/CMakeFiles/caffe2.dir/all] Error 2
Apr 04 02:40:54 make[1]: *** Waiting for unfinished jobs....
Apr 04 02:40:54 CMakeFiles/Makefile2:6159: recipe for target 'caffe2/CMakeFiles/caffe2.dir/all' failed
Apr 04 02:40:55 Compiling  all_reduce.cu                       > /var/lib/jenkins/workspace/build/nccl/obj/coll

[facebook-github-bot]

This pull request has been merged in ef779b3.