#include "petscksp.h" PetscErrorCode KSPGetConvergedReason(KSP ksp,KSPConvergedReason *reason)Not Collective
Possible values for reason: See also manual page for each reason
KSP_CONVERGED_RTOL (residual 2-norm decreased by a factor of rtol, from 2-norm of right hand side)
KSP_CONVERGED_ATOL (residual 2-norm less than abstol)
KSP_CONVERGED_ITS (used by the preonly preconditioner that always uses ONE iteration, or when the KSPConvergedSkip() convergence test routine is set.
KSP_CONVERGED_CG_NEG_CURVE (see note below)
KSP_CONVERGED_CG_CONSTRAINED (see note below)
KSP_CONVERGED_STEP_LENGTH (see note below)
KSP_CONVERGED_ITERATING (returned if the solver is not yet finished)
KSP_DIVERGED_ITS (required more than its to reach convergence)
KSP_DIVERGED_DTOL (residual norm increased by a factor of divtol)
KSP_DIVERGED_NANORINF (residual norm became Not-a-number or Inf likely due to 0/0)
KSP_DIVERGED_BREAKDOWN (generic breakdown in method)
KSP_DIVERGED_BREAKDOWN_BICG (Initial residual is orthogonal to preconditioned initial residual. Try a different preconditioner, or a different initial Level.)
The values KSP_CONVERGED_CG_NEG_CURVE, KSP_CONVERGED_CG_CONSTRAINED, and KSP_CONVERGED_STEP_LENGTH are returned only by the special KSPCGNASH, KSPCGSTCG, and KSPCGGLTR solvers which are used by the SNESNEWTONTR (trust region) solver.