Matrix multiply slices of 3d Matricies

2013 2 5
3 个回答
回答已采纳
4 次查看（30 天）

0 个投票

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.

请先登录，再回答此问题。

 采纳的回答

Jill Reese
Jill Reese 2013-9-9

1 个投票

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

更多回答（2 个）

James Tursa
James Tursa 2013-2-14
编辑：James Tursa 2013-2-14

2 个投票

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:
http://www.mathworks.com/matlabcentral/fileexchange/25977-mtimesx-fast-matrix-multiply-with-multi-dimensional-support
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:
http://www.mathworks.com/matlabcentral/fileexchange/37515-mmx-multithreaded-matrix-operations-on-n-d-matrices
Azzi Abdelmalek
Azzi Abdelmalek 2013-2-5
编辑：Azzi Abdelmalek 2013-2-5

0 个投票

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 个评论
显示 5更早的评论 隐藏 5更早的评论

Sean de Wolski
Sean de Wolski 2013-2-5
Could also use a parfor loop since each iteration is independent of others.
Dan Ryan
Dan Ryan 2013-2-5
I was hoping to see some fully parallel version that could be implemented in one shot on the gpu. This would mean no looping constructs.
Azzi Abdelmalek
Azzi Abdelmalek 2013-2-5
I don't see how you could do it without a for loop.
Sean de Wolski
Sean de Wolski 2013-2-5
What's wrong with a loop?
Dan Ryan
Dan Ryan 2013-2-5
编辑：Dan Ryan 2013-2-5
Big slowdown... for example:
A = gpuArray.rand(1000, 100, 100, 'single');
B = gpuArray.rand(1000, 100, 'single');
C = gpuArray.zeros(1000, 100, 100, 'single');
Compare
for idx = 1:100
C(:, :, idx) = A(:, :, idx).*B;
end
with
C = bsxfun(@times, A, B);
There is about a factor of 50 slowdown with the for loop.
Azzi Abdelmalek
Azzi Abdelmalek 2013-2-5
编辑：Azzi Abdelmalek 2013-2-5
bsxfun don't work with
n=3;
m=4;
k=5;
p=2;
A=rand(n,m,k)
B=rand(m,p,k)
C = bsxfun(@times, A, B);
Jill Reese
Jill Reese 2013-2-14
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

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

产品

标签

Community Treasure Hunt

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

Start Hunting!

Translated by