Error in calculating similarity，get -nan

C++
1

my code as follows：

at::Tensor output1 = model_.forward({inputs}).toTensor();

float ttt[128];

// Some assignment operations

auto output2 = torch::from_blob(ccc, {1,128});

at::Tensor score = at::cosine_similarity(output1, output2);

return score.item();

got -nan return

How to fix it ?