How to speed up this loops?

1 次查看（过去 30 天）

显示更早的评论

Alex Kurek 2016-6-1

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/286848-how-to-speed-up-this-loops

回答： Ahmed Rashid 2016-6-2

采纳的回答： Ahmed Rashid

在 MATLAB Online 中打开

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更早的评论隐藏 2更早的评论

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 2016-6-2

在 MATLAB Online 中打开

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.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Ahmed Rashid 2016-6-2

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/286848-how-to-speed-up-this-loops#answer_224251

在 MATLAB Online 中打开

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 .