prometheus related question,

[Ryan Yan]

Hi all,
I did a numerical experiment of ksp solve on a large sparse matrix.

For the first step, I load the matrix from petsc readable files. If I load
the matrix as a MPIAIJ matrix and then apply the prometheus preconditioner
with GMRES, it will not converge in 10000 iterations.

However, if I load the matrix as a MPIBAIJ matrix and then apply the
prometheus preconditioner  with GEMRES, it will converge with in 800
iterations

Can anyone please provide some hints on how to explain this numerical
result.

Thanks a lot,

Yan
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