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Sum over cell array of sparse matrices

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Gobi
Gobi on 2 Apr 2017
Commented: Gobi on 2 Apr 2017
I have 100 sparse matrices of size N by N, where N=65536.
They have about 5500000 nonzero elements(0.13% of N^2) close to the diagonal.
They are stored in a cell array, S{1}, ... , S{100}, and I want to compute the sum S{1}+...+S{100}.
Sum=sparse(N,N);
for i=1:100
Sum=Sum+S{i};
end
The above for loop code took about 25 seconds. Is there any way to optimize this code?

Answers (1)

Stalin Samuel
Stalin Samuel on 2 Apr 2017
v1=[S{1:100}];
Sum=sum(v1);
  1 Comment
Gobi
Gobi on 2 Apr 2017
This code gives a 1 by N*100 vector. v1 is a matrix stacking S{:}, and just summing up is not what I want.

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