Sets the function to be used to determine convergence.
ksp - iterative context obtained from
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#
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.