The function to get size of the tensor?

1

So I need to get the size of a list of tensors… that’s right, [tensor_1, tensor_2, tensor_3]; apparently, .size() will not work for this, so I need to use map function eventually I guess. But what’s the function to get the size of the tensor?

2

I guess you can use a lambda to do this: lambda t: t.size() ?

3

call up lambda each time will be slow tho

4

Not sure it will be slower than any other python invocation.
Why would it be so slow?

5

Basically everytime (in a loop) you use lambda, you are basically defining a function again. So predefine a function and use it later will be much more efficient than lambda.

6

Fun fact, the lambda is actually significantly faster than creating a function and reusing it :slight_smile:

In [1]: import torch

In [2]: def gs(t):
   ...:     return t.size()
   ...:

In [3]: t = torch.rand(10, 3, 2)

In [4]: %timeit gs(t)
692 ns ± 12.6 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

In [5]: %timeit gs(t)
740 ns ± 5.03 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

In [6]: %timeit lambda x: x.size()
228 ns ± 3.08 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

In [7]: %timeit lambda x: x.size()
235 ns ± 3.41 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
2 Likes