PCGetOperators

Output Parameters

Notes

Alternative usage: If the operators have NOT been set with KSP/PCSetOperators() then the operators are created in PC and returned to the user. In this case, if both operators mat and pmat are requested, two DIFFERENT operators will be returned. If only one is requested both operators in the PC will be the same (i.e. as if one had called KSP/PCSetOperators() with the same argument for both Mats). The user must set the sizes of the returned matrices and their type etc just as if the user created them with MatCreate(). For example,

        KSP/PCGetOperators(ksp/pc,&Amat,NULL); is equivalent to

          set size, type, etc of Amat

        MatCreate(comm,&mat);

        KSP/PCSetOperators(ksp/pc,Amat,Amat);

        PetscObjectDereference((PetscObject)mat);

          set size, type, etc of Amat

and

        KSP/PCGetOperators(ksp/pc,&Amat,&Pmat); is equivalent to

          set size, type, etc of Amat and Pmat

        MatCreate(comm,&Amat);

        MatCreate(comm,&Pmat);

        KSP/PCSetOperators(ksp/pc,Amat,Pmat);

        PetscObjectDereference((PetscObject)Amat);

        PetscObjectDereference((PetscObject)Pmat);

          set size, type, etc of Amat and Pmat

The rational for this support is so that when creating a TS, SNES, or KSP the hierarchy of underlying objects (i.e. SNES, KSP, PC, Mat) and their livespans can be completely managed by the top most level object (i.e. the TS, SNES, or KSP). Another way to look at this is when you create a SNES you do not NEED to create a KSP and attach it to the SNES object (the SNES object manages it for you). Similarly when you create a KSP you do not need to attach a PC to it (the KSP object manages the PC object for you). Thus, why should YOU have to create the Mat and attach it to the SNES/KSP/PC, when it can be created for you?

See Also

Level

Location

Examples