OK I take it that randperm is fine.
Actually I just found the slow performance of my code was due to
something else. Thanks for your attention.
On 2014年10月17日 11:46, Kevin Squire wrote:
I'm curious how much faster you expect it to be? Your example shows is
that permuting 100 indices, an array access, and a sum take about 70
times longer than an array access and a sum by themselves. Seems
reasonable to me...
Kevin
On Thursday, October 16, 2014, K Leo <[email protected]
<mailto:[email protected]>> wrote:
I need to permute the indexes of an array, so I found function
randperm very convenient. But it turns out very slow. The
following test shows time increased 60 times. Is there an
alternative to permute an array?
-------------
tic()
f=0.
A=[1:100]
for i=1:10000000
f += A[20]
end
toc()
elapsed time: 0.891431009 seconds
-------------
tic()
f=0.
A=[1:100]
for i=1:10000000
A = randperm(100)
f += A[20]
end
toc()
elapsed time: 60.348117087 seconds
