[petsc-dev] Performance of Petsc Cholesky vs LU

[Dave Nystrom]

I have a resistive mhd code that I have recently interfaced to petsc which
has 7 linear solves that are all symmetric.  I recently tried using -pc_type
cholesky -ksp_type preonly for a run and found that it was taking about 6
times as long per linear solve as when I was using -pc_type lu -ksp_type
preonly.  I was wondering if that was reasonable behavior.  I would not have
thought that using a cholesky direct solve would take longer than an LU
direct solve in petsc for the serial case and was hoping it would be faster.
Does this behavior seem reasonable?

Thanks,

Dave

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Dave Nystrom

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