KSPSetFromOptions

Sets KSP options from the options database. This routine must be called before KSPSetUp() if the user is to be allowed to set the Krylov type.

#include "petscksp.h" 
PetscErrorCode PETSCKSP_DLLEXPORT KSPSetFromOptions(KSP ksp)

Collective on KSP

ksp -the Krylov space context

                      convergence test (say you always want to run with 5 iterations) to

                      save on communication overhead

                   preconditioned - default for left preconditioning

                   unpreconditioned - see KSPSetNormType()

                   natural - see KSPSetNormType()

	-ksp_max_it	- maximum number of linear iterations
	-ksp_rtol rtol	- relative tolerance used in default determination of convergence, i.e. if residual norm decreases by this factor than convergence is declared
	-ksp_atol abstol	- absolute tolerance used in default convergence test, i.e. if residual norm is less than this then convergence is declared
	-ksp_divtol tol	- if residual norm increases by this factor than divergence is declared
	-ksp_converged_use_initial_residual_norm	- see KSPDefaultConvergedSetUIRNorm()
	-ksp_converged_use_min_initial_residual_norm	- see KSPDefaultConvergedSetUMIRNorm()
	-ksp_norm_type	- none - skip norms used in convergence tests (useful only when not using
	-ksp_constant_null_space	- assume the operator (matrix) has the constant vector in its null space
	-ksp_test_null_space	- tests the null space set with KSPSetNullSpace() to see if it truly is a null space
	-ksp_knoll	- compute initial guess by applying the preconditioner to the right hand side
	-ksp_monitor_cancel	- cancel all previous convergene monitor routines set
	-ksp_monitor <optional filename>	- print residual norm at each iteration
	-ksp_monitor_draw	- plot residual norm at each iteration
	-ksp_monitor_solution	- plot solution at each iteration
	-ksp_monitor_singular_value	- monitor extremem singular values at each iteration

To see all options, run your program with the -help option or consult the users manual.

KSP, set, from, options, database