Sliced Variables in "parfor"
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I'd like to run a loop using parfor similar to this:
A = zeros(10,10,10,10);
parfor i = 1:100
ind = ceil(rand(1,4)*10);
A(ind) = A(ind) + 1;
end
This yields to an error due to the way indices of A is being defined in each iteration. I understand that one workaround can be to save the "ind" values in each iteration in a temporary variable and use them in a later regular loop to update the matrix A. But I was wondering if there is any way that lets me do the whole thing in a single parfor loop. In my case the matrices and indices that I'll be working with are so large that I can't save them for use in a later loop.
Thank you all!
1 commentaire
Matt J
le 31 Déc 2016
Are you sure you didn't really mean as follows?
parfor i = 1:100
ind = ceil(rand(1,4)*10);
i=ind(1);
j=ind(2);
k=ind(3);
l=ind(4);
A(i,j,k,l) = A(i,j,k,l) + 1;
end
Réponses (1)
Matt J
le 31 Déc 2016
Suppose you wanted to do this 5 million times:
A = zeros(10,10,10,10);
M=5;
N=1e6;
parfor i = 1:M
subs = ceil(rand(N,4)*10);
A=A+accumarray(subs,1,size(A));
end
Obviously there are different possible choices of partitioning parameters M,N. You want to make N as large as your RAM reasonably allows because that will use the most vectorization.
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