How to vectorize this "for" loop, or parallel it.
显示 更早的评论
fun = @(x,y) x + x.*y;
N = 1e3;
K = zeros(N);
for i = 1:N
for j = i:N
K(i,j) = fun(i, j);
end
end
回答（2 个）
Azzi Abdelmalek
2014-1-23
编辑：Azzi Abdelmalek
2014-1-23
fun = @(x,y) x + x.*y;
N=1000
[y,x]=meshgrid(1:N,1:N);
out=triu(fun(x,y))
2 个评论
Azzi Abdelmalek
2014-1-23
编辑：Azzi Abdelmalek
2014-1-23
N=4000;
tic
fun = @(x,y) x + x.*y;
[y,x]=meshgrid(1:N,1:N);
f=triu(fun(x,y));
toc
tic
K = zeros(N);
for i = 1:N
for j = i:N
K(i,j) = fun(i, j);
end
end
toc
isequal(f,K)
Elapsed time is 0.193062 seconds.
Elapsed time is 2.421795 seconds.
chen
2014-1-23
K=(1:N).'*(2:N+1);
1 个评论
Matt J
2014-1-23
Or,
K=bsxfun(@times,(1:N).', 2:N+1);
On my machine, this is faster than straight multiplcation for some weird reason!!
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