MATLAB: How to speedup mean and std calculation on GPU

arrayfungpugpuarraymeanstd

Hello everyone, I am looking a way to speed up mean and std calculation on GPU. I run this code and it does take quite some time to complete, compared to the one if I do not use gpuArray. Maybe somebody would have any idea?
 g_p is gpuArray with matrix of (1000000,5)
   for q=1:n1-d
    x2=g_p(d-w+q-1:d+q-2,:);
mean_x=mean(x2);
    std_x=std(x2);
     R = bsxfun(@minus,x2,mean_x);
    x3=bsxfun(@rdivide,R,std_x)
  end
  
///////////
or x3=arrayfun(@norm,x2)?

Best Answer

To calculate the standard deviation, the mean must be calculated again. Try to combine this:
x2     = g_p(d-w+q-1:d+q-2,:);
mean_x = sum(x2, 1) / w;
xc     = x2 - mean_x;                % Auto-expand: >= R2016b
% xc   = bsxfun(@minus, x2, mean_x);
std_x  = vecnorm(xc) / sqrt(s - 1);  % vecnorm: >= R2017b
% std_x  = sqrt(sum(xc .* xc, 1)) / sqrt(s - 1);
for the mean only the first and the last element changed between the iterations. Use this detail:
mean_x = sum(g_p(d-w:d-1, :) / w;  % For q=1
for q = 1:n1-d
   ...
   mean_x = mean_x - (g_p(d-w+q-1, :) + g_p(d+q-1, :)) / w;
end
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