How to speed up this loops?

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Alex Kurek
Alex Kurek 2016-6-1
回答： Ahmed Rashid 2016-6-2
Hi,
Is there a way to speed up this?
maxN = 120;
x = -30:0.1:30;
xElements = numel(x);
u_mn = zeros(xElements, xElements);
for m = -maxN:2:maxN
for i = 1 : xElements
for j = 1 : xElements
u_mn(i, j) = sqrt((n+1)/pi) * besselj(m+1, 2*sqrt(x(i)^2 + x(j)^2)) / sqrt(x(i)^2 + x(j)^2)^(m+1) * (x(i) + 1i*x(j))^m;
end
end
end
Best regards, Alex
  4 个评论
显示 2更早的评论
Walter Roberson
Walter Roberson 2016-6-1
You do not store the results for each different m, and you are not summing them or anything like that, so the effect is as if you had only done the final m value.
Alex Kurek
Alex Kurek 2016-6-2
Thanky you, obviously, you are right. the middle line in the loops should look like this:
for m = -maxN:2:maxN
for i = 1 : xElements
for j = 1 : xElements
u_mn(i, j) = u_mn(i, j) + sqrt((n+1)/pi) * besselj(m+1, 2*sqrt(x(i)^2 + x(j)^2)) / sqrt(x(i)^2 + x(j)^2)^(m+1) * (x(i) + 1i*x(j))^m;
end
end
end
But still, how to speed this up? Its not working to fast right now.

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采纳的回答

Ahmed Rashid
Ahmed Rashid 2016-6-2
You can create a mex function of your firstTestFunct by
xx = 1;
codegen firstTestFunct -args {xx, xx, xx, xx}
You need to do it only once. It will generate a mex file. To call the generated mex file, you just need to replace firstTestFunct with firstTestFunct_mex .

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