Slow sparse matrix multiplication

[Richard Hindmarsh]

Matrix-matrix multiplication for very sparse matrices seems a bit slow. 
The results below apply also to very sparse matrix/vector multiplications.

CVS downloaded 9th March 2005, x86-64, gcc3.3.2

octave:17> a = sparse(10000,10000);
octave:18> a(1,1) = 1;

octave:19> tic;a*a;toc
ans = 0.73152
octave:20> tic;a+a;toc
ans = 0.00047300

Given that the number of f.p. operations are the same, one would expect 
similar timings. I'd be happy to have a look at the matrix 
multiplication routines if pointed too them.

Richard



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