I need to optimize my matlab code through vectorization

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I need to vectorize this loop in code.. can someone guide?

function X = IDWT2DCT(x,Dct_matrix,IW_matrix)
[K,MN]=size(x);
block_size = 8;
X = zeros(block_size,block_size,K);
temp = zeros(block_size,block_size);
y = (Dct_matrix'*x);
for k = 1:K
    temp = reshape(y(k,:),block_size,block_size);
    X(:,:,k) = IW_matrix*temp*IW_matrix';    
end

*****Speed is not issue, i just need to vanish this loop****** [EDITED, Jan, Code formatted]

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Image Analyst 2015-4-16

I agree with Jan that the loop takes virtually no time, unless K is huge, and I'm talking billions. Looping a few hundred thousand or a few million times takes like a microsecond. What is the value of K? What are the dimensions of Y and x?

Abeera Tariq 2015-4-17

I need to implement the whole code on GPU, issue is that there are many loops inside loops .. so as an initiative i took inner most loop so that i can move to outer most loop..

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Answer 1

Jan 2015-4-16

1 个投票

I hesitate to invest any period of time when I cannot see any benefit. You ask for an "optimization", but the code will not be better in any way if it is vectorized. Therefore I'm convinced, that I cannot "optimize" it, especially when speed does not matter. If you want to have more complex for debugging and most likely faster as a side-effect, try these marvelous functions:

Please note, that "optimizing" code, which is not a bottleneck of a program is a known anti-pattern of programming. See http://en.wikipedia.org/wiki/Anti-pattern -> "premature optimization" and http://en.wikipedia.org/wiki/Optimization_(computer_science)#When_to_optimize

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Abeera Tariq 2015-4-16

I need to implement this on gpu nd there r many loops inside loops so i started removing these loops through vectorization.. :(

James Tursa 2015-4-16

编辑：James Tursa 2015-4-16

If you are implementing this on a GPU then why not work with a BLAS library to do the matrix multiplies? E.g.,

https://developer.nvidia.com/cublas

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