mtimesm, an efficient nD matrix multiplication routine.

Version 1.0.6 (3.11 KB) by wfH
A wrapper of `MTIMESX` and `PAGEMTIMES`. Created for people who have old matlab or have difficulties in compiling mex-file.
83 Downloads
Updated 30 Jun 2022

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MTIMESX (`PAGEMTIMES`) is a very efficient matrix multiply routine for n-Dimensional (nD, n > 2) arrays.
However, you have to update your MATLAB (`PAGEMTIMES` was introduced in R2020b), or build a mex-file.
So, I created this function (m-file) for people who have only old matlab or have difficulties in compiling mex-file.
This function follows the same behaviour as MTIMESX (`PAGEMTIMES`).
Run the following codes for demonstration.
ctest = 2000;
nfs1 = 45;
nfs2 = 55;
nks1 = 5;
nks2 = 7;
A = rand(nks1, nks1, nfs1, nfs2);
B = rand(nks2, nks1, nfs1, nfs2);
tic;
for ii = 1:ctest
C1 = zeros(nks1, nks2, nfs1, nfs2);
for ff = 1:nfs1
for gg = 1:nfs2
C1(:,:, ff, gg) = conj(A(:,:, ff, gg)).'*B(:,:, ff, gg).';
end
end
end
t1 = toc
tic, for jj = 1:ctest, C2 = mtimesx(A, 'c', B, 't');end, t2 =toc
tic; for kk = 1:ctest, C3 = mtimesm(A, 'c', B, 't', true);end, t3 = toc
tic; for oo = 1:ctest, C4 = pagemtimes(A, 'c', B, 't');end, t4 = toc
max(abs(C1(:)-C2(:)))
max(abs(C1(:)-C3(:)))
max(abs(C1(:)-C4(:)))
% on my notebook (i7-8550u), t1 ~17 sec; t2 ~1.3 sec; t3 ~3.8 sec; t4 ~0.39 sec.
% `PAGEMTIMES` is the fast in this case.

Cite As

wfH (2024). mtimesm, an efficient nD matrix multiplication routine. (https://www.mathworks.com/matlabcentral/fileexchange/82099-mtimesm-an-efficient-nd-matrix-multiplication-routine), MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R2020a
Compatible with any release
Platform Compatibility
Windows macOS Linux

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Version Published Release Notes
1.0.6

feat: supports "string".
feat: add parameter that specifies to use `pagemtimes` (`mtimesx`) or not.
doc: update demo

1.0.5

add wrapper of `pagemtimes`.

1.0.1

add example and result of comparison .

1.0.0