Fast matrix multiplication in loop
3 views (last 30 days)
Show older comments
Dear All,
I have two matrices with dimensions 3x3 and E6x3. I need to multiply each row of the latter with the former. It's like
a=rand(3,3);
b=(1000000,3);
for i=1:size(b,1)
c=a*b(i,:)';
end
However, this step takes hours to be done. I wonder if there is any faster way to do this.
Cheers.
1 Comment
Accepted Answer
Azzi Abdelmalek
on 7 Feb 2014
Edited: Azzi Abdelmalek
on 7 Feb 2014
a=rand(3,3);
b=rand(100,3);
n=size(a,2);
m=size(b,1);
c=zeros(m,n);
for i=1:size(b,1)
c(i,:)=a*b(i,:)';
end
%or simply
c=(a*b')'
0 Comments
More Answers (2)
Jos (10584)
on 7 Feb 2014
Two options:
1. pre-allocate C to avoid memory allocation in each iteration
C = zeros(N, ..) % pre-allocation
for k = 1:N,
C(k,:) = ..
end
2. Use BSXFUN
See Also
Categories
Find more on Loops and Conditional Statements in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!