multifrontal accuracy

[wavedreamer0822]

I attempted to solve a complex double-precision sparse matrix using the multifrontal direct method and found that when the matrix dimension exceeds 100,000, the accuracy drops sharply. May I ask if STRUMPACK does not support matrices of such large scale?

[pghysels]

That must be a bug somewhere. 100,000 is not particularly large for a sparse matrix. Is it very sparse?

[wavedreamer0822]

yes its average bandwidth is about 20

[pghysels]

You can try a different permutation for numerical stability:

STRUMPACK/src/StrumpackOptions.hpp

Line 530 in cfba574

void set_matching(MatchingJob job) { matching_job_ = job; }

A different fill-reducing ordering could also help.

Or enable replacement of tiny pivots:

STRUMPACK/src/StrumpackOptions.hpp

Line 709 in cfba574

void enable_replace_tiny_pivots() { replace_tiny_pivots_ = true; }