PCFieldSplitSchurGetSubKSP

Gets the KSP contexts used inside the Schur complement based PCFIELDSPLIT

Synopsis

#include "petscpc.h" 
PetscErrorCode PCFieldSplitSchurGetSubKSP(PC pc, PetscInt *n, KSP *subksp[])

Collective

Input Parameter

• pc - the preconditioner context

Output Parameters

• n - the number of splits

• subksp - the array of KSP contexts

Notes

After PCFieldSplitSchurGetSubKSP() the array of KSPs is to be freed by the user with PetscFree() (not the KSP just the array that contains them).

You must call PCSetUp() before calling PCFieldSplitSchurGetSubKSP().

If the fieldsplit type is of type PC_COMPOSITE_SCHUR, it returns (in order)

• 1 - the KSP used for the (1,1) block

• 2 - the KSP used for the Schur complement (not the one used for the interior Schur solver)

• 3 - the KSP used for the (1,1) block in the upper triangular factor (if different from that of the (1,1) block).

It returns a null array if the fieldsplit is not of type PC_COMPOSITE_SCHUR; in this case, you should use PCFieldSplitGetSubKSP().

Fortran Notes

You must pass in a KSP array that is large enough to contain all the local KSPs. You can call PCFieldSplitSchurGetSubKSP(pc,n,PETSC_NULL_KSP,ierr) to determine how large the KSP array must be.

Developer Notes

There should be a PCFieldSplitRestoreSubKSP() instead of requiring the user to call PetscFree()

Should the functionality of PCFieldSplitSchurGetSubKSP() and PCFieldSplitGetSubKSP() be merged?

The Fortran interface should be modernized to return directly the array of values.

See Also

Solving Block Matrices with PCFIELDSPLIT, PC, PCFIELDSPLIT, PCFieldSplitSetFields(), PCFieldSplitSetIS(), PCFieldSplitGetSubKSP()

Level

advanced

Location

src/ksp/pc/impls/fieldsplit/fieldsplit.c

Examples

src/dm/impls/stag/tutorials/ex4.c

Implementations

PCFieldSplitSchurGetSubKSP_FieldSplit() in src/ksp/pc/impls/fieldsplit/fieldsplit.c

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