Best way to iterate through tensors

1

Currently, I’ve seen 2 ways of iterating through a tensor.
1.

for v in TENSOR:
    pass

a = TENSOR.unbind(0)
for v in a:
    pass

I have 3 questions:

  1. Which of these 2 are faster in Python?
  2. Which of these 2 are faster in TouchScript(I’ve seen the custome lstm uses the second way).
  3. Following 2, which of the following is faster in C++:

First.

for(int i=0;i<TENSOR.size(0);++i){
    auto v=TENSOR[i];
}

Second.

auto vec=TENSOR.unbind(0);
for(int i=0;i<vec.size();++i){
    auto v=vec[i];
}

Thanks