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for loop and data in GPU memory

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Milos
Milos on 7 Nov 2012
If the for loop is parallelizable, does the Parallel Computing Toolbox execute for loop in a parallel fashion when it is acting on data stored in GPU memory?
  2 Comments
Milos
Milos on 8 Nov 2012
Suppose that f is a time-consuming function to compute, and that you want to compute its value on each element of array A and place the corresponding results in array B
A = gpuArray(X);
for i = 1:length(A)
B(i) = f(A(i));
end
Because the loop iteration can occur in parallel, this evaluation could complete much faster if for loop run in parallel on the GPU - in similar fashion like parfor loop is executed. My question is does this happen automatically or for loop is executed in the ordinary non-parallel fashion?

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Accepted Answer

Jill Reese
Jill Reese on 9 Nov 2012
The for loop is not performed in parallel when you write code like this:
A = gpuArray(X);
for i = 1:length(A)
B(i) = f(A(i));
end
However, if your function f contains only elementwise operations, then you could achieve more parallelism by using arrayfun like so:
B = arrayfun(@f, A);

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