KSPSetTolerances#

Sets the relative, absolute, divergence, and maximum iteration tolerances used by the default KSP convergence testers.

Synopsis#

#include "petscksp.h" 
#include "petscmat.h" 
PetscErrorCode KSPSetTolerances(KSP ksp, PetscReal rtol, PetscReal abstol, PetscReal dtol, PetscInt maxits)

Logically Collective

Input Parameters#

ksp - the Krylov subspace context
rtol - the relative convergence tolerance, relative decrease in the (possibly preconditioned) residual norm
abstol - the absolute convergence tolerance absolute size of the (possibly preconditioned) residual norm
dtol - the divergence tolerance, amount (possibly preconditioned) residual norm can increase before KSPConvergedDefault() concludes that the method is diverging
maxits - maximum number of iterations to use

Options Database Keys#

-ksp_atol - Sets abstol
-ksp_rtol - Sets rtol
-ksp_divtol - Sets dtol
-ksp_max_it - Sets maxits

Notes#

All parameters must be non-negative.

Use PETSC_CURRENT to retain the current value of any of the parameters. The deprecated PETSC_DEFAULT also retains the current value (though the name is confusing).

Use PETSC_DETERMINE to use the default value for the given KSP. The default value is the value when the object’s type is set.

For dtol and maxits use PETSC_UMLIMITED to indicate there is no upper bound on these values

See KSPConvergedDefault() for details how these parameters are used in the default convergence test. See also KSPSetConvergenceTest() for setting user-defined stopping criteria.

Fortran Note#

Use PETSC_CURRENT_INTEGER, PETSC_CURRENT_REAL, PETSC_DETERMINE_INTEGER, or PETSC_DETERMINE_REAL

Level#

intermediate

Location#

src/ksp/ksp/interface/itfunc.c

Examples#

src/ksp/ksp/tutorials/ex2f.F90
src/ksp/pc/tutorials/ex3.c
src/ksp/ksp/tutorials/ex86.c
src/ksp/ksp/tutorials/ex1f.F90
src/ksp/ksp/tutorials/ex18.c
src/ksp/ksp/tutorials/ex2.c
src/ksp/ksp/tutorials/ex15f.F90
src/ksp/ksp/tutorials/ex7f.F90
src/ksp/ksp/tutorials/ex52f.F90
src/ksp/ksp/tutorials/ex6.c

Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages