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Interfaces like KSPSetOperators (https: //urldefense. us/v3/__https: //petsc. org/main/manualpages/KSP/KSPSetOperators/__;!!G_uCfscf7eWS!YINsVNEe8TcsVMY3AVwkS1hf46fWdiKi5JNOe9560N5QG1LPQyjMQgodivpJtg1IwxHgRR3_V3uHWG4h2AI$) have Amat and Pmat arguments.
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</head><body><pre style="font-family: sans-serif; font-size: 100%; white-space: pre-wrap; word-wrap: break-word">Interfaces like KSPSetOperators (<a href="https://urldefense.us/v3/__https://petsc.org/main/manualpages/KSP/KSPSetOperators/__;!!G_uCfscf7eWS!YINsVNEe8TcsVMY3AVwkS1hf46fWdiKi5JNOe9560N5QG1LPQyjMQgodivpJtg1IwxHgRR3_V3uHWG4h2AI$">https://urldefense.us/v3/__https://petsc.org/main/manualpages/KSP/KSPSetOperators/__;!!G_uCfscf7eWS!YINsVNEe8TcsVMY3AVwkS1hf46fWdiKi5JNOe9560N5QG1LPQyjMQgodivpJtg1IwxHgRR3_V3uHWG4h2AI$</a>) have Amat and Pmat arguments. The Amat is used as the Krylov operator and the Pmat is used for preconditioning.
In a general sense, Pmat is just whatever data is to be used by the preconditioner, though for algebraic preconditioners, it's usually regarded as an assembled matrix. If you're not using PCShell, then you need to think about what the preconditioner needs (conceptually or check the code).
Raju Mandhapati <mandhapati.raju@convergecfd.com> writes:
> Hello,
>
> I want to use my own custom matrix vector multiplication routine (which
> will use finite difference method to calculate it). I will supply a matrix
> but that matrix should be used only for preconditioner and not for matrix
> vector multiplication. Is there a way to do it?
>
> thanks
> Raju.
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