[petsc-users] multiplication of large matrices using MatMatMult

[Jed Brown]

On Mon, Jan 2, 2012 at 17:45, Reza Madankan <rm93 at buffalo.edu> wrote:

> Yes, the matrix is dense. So, you mean that there is no way to evaluate
> the matrix, exactly?


You can evaluate it, but there is almost always a way to get the "science"
result without computing all the entries. Such an algorithm would be faster.


> .... I have run the code for smaller size of Ypcq and it's working. But
> for larger sizes I get the error that I mentioned.


It's possible that the corruption is caused by some integer overflow and
not from actually running out of memory, but it's definitely worth checking
that smaller sizes do not have some small error that is detectable by
Valgrind (e.g. an uninitialized variable that happens to be equal to 0 at
small sizes, or an off-by-one error that does not cause problems for small
sizes).
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