Matrix multiply slices of 3d Matricies

61 views (last 30 days)
Dan Ryan
Dan Ryan on 5 Feb 2013
Given two 3d matricies, A and B with
size(A) = (n, m, k)
and
size(B) = (m, p, k)
perform matrix multiplications on each slice obtained by fixing the last index, yielding a matrix C with
size(C) = (n, p, k).
To clarify, we would have
C(:, :, 1) = A(:, :, 1)*B(:, :, 1), ..., C(:, :, k) = A(:, :, k)*B(:, :, k).
I need to do this with gpuArrays in the most efficient manner possible.

Accepted Answer

Jill Reese
Jill Reese on 9 Sep 2013
If you have MATLAB R2013b, you can use the new gpuArray pagefun function like so:
C = pagefun(@mtimes, A, B);

More Answers (2)

James Tursa
James Tursa on 14 Feb 2013
Edited: James Tursa on 14 Feb 2013
If you are not restricted to gpuArrays you can do this:
C = mtimesx(A,B);
The MTIMESX function passes pointers to the slice data to BLAS library functions in the background, so it is pretty fast. You can find MTIMESX here:
MTIMESX is not yet multi-threaded across the third dimension (but an update is in the works). A nD matrix multiply multi-threaded on the third dimension called MMX can also be used:
C = MMX('mult', A, B);
MMX can be found here:
  1 Comment
Dan Ryan
Dan Ryan on 14 Feb 2013
great suggestion, I will keep an eye on this project

Sign in to comment.


Azzi Abdelmalek
Azzi Abdelmalek on 5 Feb 2013
Edited: Azzi Abdelmalek on 5 Feb 2013
n=3;
m=4;
k=5;
p=2;
A=rand(n,m,k)
B=rand(m,p,k)
C=zeros(n,p,k)
for ii=1:k
C(:,:,ii)=A(:,:,ii)*B(:,:,ii)
end
  7 Comments
Jill Reese
Jill Reese on 14 Feb 2013
Dan,
Can you elaborate on the sizes of m, n , k, and p that you are interested in? It would be useful to know a ballpark number for the size of problem you want to solve. Do you have many small page sizes, a few large pages, or something else?
Thanks,
Jill

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!