KSPSetConvergenceTest#

Sets the function to be used to determine convergence.

Synopsis#

#include "petscksp.h" 
#include "petscmat.h" 
PetscErrorCode KSPSetConvergenceTest(KSP ksp, PetscErrorCode (*converge)(KSP, PetscInt, PetscReal, KSPConvergedReason *, void *), void *cctx, PetscErrorCode (*destroy)(void *))

Logically Collective

Input Parameters#

ksp - iterative context obtained from KSPCreate()
converge - pointer to the function
cctx - context for private data for the convergence routine (may be null)
destroy - a routine for destroying the context (may be null)

Calling sequence of `converge`#

PetscErrorCode converge(KSP ksp, PetscInt it, PetscReal rnorm, KSPConvergedReason *reason, void *mctx)

ksp - iterative context obtained from KSPCreate()
it - iteration number
rnorm - (estimated) 2-norm of (preconditioned) residual
reason - the reason why it has converged or diverged
cctx - optional convergence context, as set by KSPSetConvergenceTest()

Calling Sequence of `destroy`#

PetscErrorCode destroy(void *cctx)

Notes#

Must be called after the KSP type has been set so put this after a call to KSPSetType(), or KSPSetFromOptions().

The default convergence test, KSPConvergedDefault(), aborts if the residual grows to more than 10000 times the initial residual.

The default is a combination of relative and absolute tolerances. The residual value that is tested may be an approximation; routines that need exact values should compute them.

In the default PETSc convergence test, the precise values of reason are macros such as KSP_CONVERGED_RTOL, which are defined in petscksp.h.