我正在为pytorch写一个c扩展，其中我需要通过索引访问一个Tensor的元素，我还需要将元素转换为标准的c类型。这里有一个简短的例子。假设我有一个2dTensora，我需要访问a[i][j]并将其转换为float。

#include <torch/extension.h>
float get(torch::Tensor a, int i, int j) {
    return a[i][j];
}

字符串
上面的代码被放入一个名为tensortest.cpp的文件中。

from setuptools import setup, Extension
from torch.utils import cpp_extension
setup(name='tensortest',
      ext_modules=[cpp_extension.CppExtension('tensortest_cpp', ['tensortest.cpp'])],
      cmdclass={'build_ext': cpp_extension.BuildExtension})

型
当我运行python setup.py install时，编译器报告以下错误

running install
running bdist_egg
running egg_info
creating tensortest.egg-info
writing tensortest.egg-info/PKG-INFO
writing dependency_links to tensortest.egg-info/dependency_links.txt
writing top-level names to tensortest.egg-info/top_level.txt
writing manifest file 'tensortest.egg-info/SOURCES.txt'
/home/trisst/.local/lib/python3.8/site-packages/torch/utils/cpp_extension.py:335: UserWarning: Attempted to use ninja as the BuildExtension backend but we could not find ninja.. Falling back to using the slow distutils backend.
  warnings.warn(msg.format('we could not find ninja.'))
reading manifest file 'tensortest.egg-info/SOURCES.txt'
writing manifest file 'tensortest.egg-info/SOURCES.txt'
installing library code to build/bdist.linux-x86_64/egg
running install_lib
running build_ext
building 'tensortest_cpp' extension
creating build
creating build/temp.linux-x86_64-3.8
x86_64-linux-gnu-gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -g -fwrapv -O2 -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -I/home/user/.local/lib/python3.8/site-packages/torch/include -I/home/user/.local/lib/python3.8/site-packages/torch/include/torch/csrc/api/include -I/home/user/.local/lib/python3.8/site-packages/torch/include/TH -I/home/user/.local/lib/python3.8/site-packages/torch/include/THC -I/usr/include/python3.8 -c tensortest.cpp -o build/temp.linux-x86_64-3.8/tensortest.o -DTORCH_API_INCLUDE_EXTENSION_H -DTORCH_EXTENSION_NAME=tensortest_cpp -D_GLIBCXX_USE_CXX11_ABI=0 -std=c++14
In file included from /home/user/.local/lib/python3.8/site-packages/torch/include/ATen/Parallel.h:149,
                 from /home/user/.local/lib/python3.8/site-packages/torch/include/torch/csrc/api/include/torch/utils.h:3,
                 from /home/user/.local/lib/python3.8/site-packages/torch/include/torch/csrc/api/include/torch/nn/cloneable.h:5,
                 from /home/user/.local/lib/python3.8/site-packages/torch/include/torch/csrc/api/include/torch/nn.h:3,
                 from /home/user/.local/lib/python3.8/site-packages/torch/include/torch/csrc/api/include/torch/all.h:7,
                 from /home/user/.local/lib/python3.8/site-packages/torch/include/torch/extension.h:4,
                 from tensortest.cpp:1:
/home/user/.local/lib/python3.8/site-packages/torch/include/ATen/ParallelOpenMP.h:84: warning: ignoring #pragma omp parallel [-Wunknown-pragmas]
   84 | #pragma omp parallel for if ((end - begin) >= grain_size)
      | 
tensortest.cpp: In function ‘float get(at::Tensor, int, int)’:
tensortest.cpp:4:15: error: cannot convert ‘at::Tensor’ to ‘float’ in return
    4 |  return a[i][j];
      |               ^
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

型
我该怎么办？