[petsc-users] Using Petsc with multiple RHS

[Alexander Grayver]

Hello,

I used to use MUMPS directly with sparse multiple RHS. Now I use MUMPS 
through PETSc interface and solution for multiple RHS takes 1.5-2 times 
longer (MatMatSolve).
My first question is whether do you use multiple RHS internally or you 
solve one-by-one?
Second guess concerns the option:
ICNTL(20) (rhs sparse pattern):                         0

It's always switched off in PETSc, however my RHS are very sparse (8-32 
nonzeros ans my system is 10^6). I can imagine that ignoring sparsity 
makes this performance difference.
Any ideas are appreciated.

Regards,
Alexander