Demonstrate value/reference copy/assignment semantics of LibTorch at::Tensor

gistfile1.txt

/*

Output:

                     operator=  reference copy (same memory)
                         copy_  value copy (different memory)
       operator= of operator[]  value copy (different memory)
                         slice  reference copy (same memory)

*/

#include <stdio.h>
#include <torch/script.h>

void TestTensorSemantics() {
	// copy, assignment, etc
	std::vector<std::pair<std::string, std::function<void(const at::Tensor& src, at::Tensor& dst)>>> tests = {
	    {"operator=", [](const at::Tensor& src, at::Tensor& dst) { dst = src; }},
	    {"copy_", [](const at::Tensor& src, at::Tensor& dst) { dst.copy_(src); }},
	    {"operator= of operator[]", [](const at::Tensor& src, at::Tensor& dst) { dst[0] = src[0]; }},
	    {"slice", [](const at::Tensor& src, at::Tensor& dst) { dst = src.slice(0, 0, 1); }},
	};

	for (auto tx : tests) {
		auto src = torch::zeros({4, 3, 1});
		auto dst = torch::zeros_like(src);
		printf("%30s  ", tx.first.c_str());
		tx.second(src, dst);

		auto src_d     = src.accessor<float, 3>();
		auto dst_d     = dst.accessor<float, 3>();
		src_d[0][0][0] = 999;
		if (dst_d[0][0][0] == 999)
			printf("reference copy (same memory)\n");
		else
			printf("value copy (different memory)\n");
	}
}

int main(int argc, char** argv) {
  TestTensorSemantics();
  return 0;
}