How to access the data of a Tensor

C++
1

Hi,
I wanted to directly access the data matrix of the Tensor to store in a primary type, e.g.a double array. I was doing this to write the Tensor to a binary file. Following this post Convert tensor into an array I tried

 torch::Tensor preds = torch::zeros({ 4,8 });
        preds.index_put_({0,1},2);
        preds.index_put_({0,3},4);
        preds.index_put_({1,7},5);
        preds.index_put_({2,5},-5);
        preds.index_put_({3,6},-3.96);
        preds.index_put_({2,6},-1e-3);
       double* mydata=preds.data_ptr<double>();

But I get sigabort every time I do this. Any ideas how to address this?
thanks!

2

You could try to initialize or transform the tensor to double as the default dtype would be float (i.e. float32).

1 Like
3

Thank you that worked! I did it like

torch::Tensor preds = torch::zeros({ 4,8 }).to(torch::kDouble);

However, I noted that although this is a 2d tensor, the data_ptr will only return a double* pointer. So I always have to do this:

double* mydata1d=preds.data_ptr<double>();

which I would read as a 1D array. I wonder if it is possible to read it in as a 2D array.

That said, I realized I can also just write the Tensor directly to a binary file like

mytensorfile.write(reinterpret_cast<char*>(&preds),4*8*sizeof(torch::kDouble));