# KSPBuildSolution#

Builds the approximate solution in a vector provided.

## Synopsis#

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


Collective

## 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 KSPGMRES this is a reasonably expensive operation and should only be used in truly needed.

KSP: Linear System Solvers, KSPGetSolution(), KSPBuildResidual(), KSP

developer

## Location#

src/ksp/ksp/interface/itfunc.c

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