petsc-3.14.5 2021-03-03
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# KSPBuildSolution

Builds the approximate solution in a vector provided. This routine is NOT commonly needed (see KSPSolve()).

### Synopsis

    #include "petscksp.h"
    #include "petscmat.h"
    PetscErrorCode  KSPBuildSolution(KSP ksp,Vec v,Vec *V)

Collective on ksp

### Input Parameter

| ctx | - iterative context obtained from KSPCreate()

### Output Parameter

Provide exactly one of

| v | - location to stash solution.
| V | - the solution is returned in this location. This vector is created internally. This vector should NOT be destroyed by the user with VecDestroy().

### Notes

This routine can be used in one of two ways

          KSPBuildSolution(ksp,NULL,&V);
       or
          KSPBuildSolution(ksp,v,NULL); or KSPBuildSolution(ksp,v,&v);

In the first case an internal vector is allocated to store the solution (the user cannot destroy this vector). In the second case the solution is generated in the vector that the user provides. Note that for certain methods, such as KSPCG, the second case requires a copy of the solution, while in the first case the call is essentially free since it simply returns the vector where the solution already is stored. For some methods like GMRES this is a reasonably expensive operation and should only be used in truly needed.

### See Also

KSPGetSolution(), KSPBuildResidual(), KSP

### Level

advanced

### Location

src/ksp/ksp/interface/itfunc.c

### Examples

src/ksp/ksp/tutorials/ex9.c.html
src/ksp/ksp/tutorials/ex2f.F90.html
src/snes/tutorials/ex12.c.html

### Implementations

KSPBuildSolution_BCGS in src/ksp/ksp/impls/bcgs/bcgs.c
KSPBuildSolution_FETIDP in src/ksp/ksp/impls/fetidp/fetidp.c
KSPBuildSolution_GCR in src/ksp/ksp/impls/gcr/gcr.c
KSPBuildSolution_AGMRES in src/ksp/ksp/impls/gmres/agmres/agmres.c
KSPBuildSolution_DGMRES in src/ksp/ksp/impls/gmres/dgmres/dgmres.c
KSPBuildSolution_FGMRES in src/ksp/ksp/impls/gmres/fgmres/fgmres.c
KSPBuildSolution_GMRES in src/ksp/ksp/impls/gmres/gmres.c
KSPBuildSolution_LGMRES in src/ksp/ksp/impls/gmres/lgmres/lgmres.c
KSPBuildSolution_PGMRES in src/ksp/ksp/impls/gmres/pgmres/pgmres.c
KSPBuildSolution_PIPEFGMRES in src/ksp/ksp/impls/gmres/pipefgmres/pipefgmres.c
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages