Apply function to each row in Torch

Question

I know that tensors have an apply method, but this only applies a function to each element. Is there an elegant way to do row-wise operations? For example, can I multiply each row by a different value?

Say

and

and I want to multiply each element in the ith row of A by the ith element of B to get

1 2 3
8 10 12
21 24 27

how would I do that?

You should take a look at this question: http://stackoverflow.com/questions/34123291/torch-apply-function-over-dimension — Alexander Lutsenko, Dec 21 '15 at 21:37

score 2 · Answer 1 · edited May 23 '17 at 10:34

2

See this link: Torch - Apply function over dimension

(Thanks to Alexander Lutsenko for providing it. I just moved it to the answer.)

edited May 23 '17 at 10:34

Community

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answered Dec 23 '15 at 14:23

Veech

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score 1 · Answer 2 · answered Dec 22 '15 at 08:26

1

One possibility is to expand B as follow:

 1  1  1
 2  2  2
 3  3  3
[torch.DoubleTensor of size 3x3]

Then you can use element-wise multiplication directly:

local A = torch.Tensor{{1,2,3},{4,5,6},{7,8,9}}
local B = torch.Tensor{1,2,3}
local C = A:cmul(B:view(3,1):expand(3,3))

answered Dec 22 '15 at 08:26

deltheil

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Thanks! Yeah, there are a few different ways to do it for my example, but I was wondering if there was a general way to apply a function to each row. I think Alexander's comment answers my first question. – Veech Dec 22 '15 at 14:38

Apply function to each row in Torch

2 Answers2