[petsc-users] Why is there MAPMPIAIJ

[Bojan Niceno]

Dear all,

I am coupling my unstructured CFD solver with PETSc.  At this moment,
sequential version is working fine, but I obviously want to migrate to MPI
parallel.  My code is MPI parallel since ages.

Anyhow, as a part of the migration to parallel, I changed the matrix type
from MATSEQAIJ to MATMPIAIJ.  The code compiled, but when I executed it one
processor, I received an error message that combination of matrix format
does not support BICG solver and PCILU preconditoner.  I took a look at the
compatibility matrix (
https://petsc.org/release/overview/linear_solve_table/#preconditioners) and
noticed that MATMPIAIJ supports only MKL CParadiso preconditioner which
seems to belong to Intel.

I did some more reading and realised that I should probably continue with
MATAIJ (which should work in sequential and parallel), but I am wondering
why would there even be MATMPIAJ if it supports only one third-party
preconditioner?

    Cheers,

    Bojan Niceno
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