Why GPU performance is worse than CPU for this code?
조회 수: 3 (최근 30일)
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clear all
close all
tic
t=9999;
X = rand( t, 'single' );
G = gpuArray( X );
isequal( gather( G ), X ) % returns true
classUnderlying( G ) % returns 'single'
G2 = G .* G
toc
tic
X = rand( t, 'single' );
G1 = X;
G3 = G1 .* G1 ;
toc
The execution time of GPU is less than CPu i5. Would anybody answer it?
댓글 수: 1
Jan
2011년 11월 27일
About "clear all" see: http://www.mathworks.com/matlabcentral/answers/16484-good-programming-practice#answer_22301
Please decide, if the "GPU performance is worse than CPU", or if "the execution time of GPU is less than CPU".
채택된 답변
Walter Roberson
2011년 11월 27일
There is a lot of overhead for sending data to a GPU. It is only faster for sufficiently big matrices.
Also, in the first one you are including the "isequal" and the "classUnderlying" in the timing, neither of which is needed for the computation. It is not fair to time different sets of activities.
추가 답변 (2개)
Jan
2011년 11월 27일
Please try this:
X = rand(1e3, 1e3, 'single' );
G = gpuArray( X );
G2 = G;
tic
for i = 1:100
G2 = G2 .* G;
end
toc
tic
G = X;
G2 = X;
for i = 1:100
G2 = G2 .* G;
end
toc
cdarling
2012년 2월 19일
there is a possibility that your GPU supports parallel.gpu.GPUArray.rand(), and it would be much faster if you construct random numbers within GPU, instead of generate and copy them into GPU
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