How large can a sparse matrix be?

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Patrick Mboma
Patrick Mboma 2015-7-22
评论： Patrick Mboma 2015-7-23
Hi,
I thought I could exploit the fact that a matrix is sparse to build a big matrix. I would like to build a sparse matrix of size 46 times 8153726976. The matrix itself is very big but only has approximately 60,000 non-zero entries. I have not succeeded even in creating a completely sparse matrix of the same size. Is there any solution to this problem?
Thanks,

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Steven Lord
Steven Lord 2015-7-22
The larger the number of columns in a sparse matrix, the more memory it consumes. Try creating a tall but thin sparse matrix instead of a short and wide matrix.
S = spalloc(8153726976, 46, 60000);
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Titus Edelhofer
Titus Edelhofer 2015-7-23
Hi Patrick,
then the result C should be relatively small. Did you try the obvious, namely
C = A' * B;
I'm not sure, but it guess that MATLAB identifies the pattern and computes the multiplication without "computing" the transpose before ...
Titus
Patrick Mboma
Patrick Mboma 2015-7-23
Titus, I have checked that what you suggested works. Matlab somehow avoids transposing the matrix before doing the multiplication. Wahoo! Now the only thing I have to make sure of is that matrix B is not too wide.
To all, Thank you so much

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