[petsc-users] understanding of the preconditioner setted from KSPSetOperators

[Mike Wick]

Hi PETSc team:

I just want to get some clarifications on the use of preconditioners in
PETSc.

Suppose I provide the Pmat as the second argument in KSPSetOperators as a
user-specified matrix and it is different from Amat, the actual matrix to
be solved. When I specify a preconditioner, say ASM, what does that mean? I
am assuming that we are doing a preonly-type thing for solving Pmat, is
that right? There is no iterative solver applied to Pmat over the
iterations.

Best,

Mike
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