petsc-3.7.5 2017-01-01

KSPBCGSLSetEll

Sets the number of search directions in BiCGStab(L).

Synopsis

#include "petscksp.h" 
PetscErrorCode  KSPBCGSLSetEll(KSP ksp, PetscInt ell)

Logically Collective on KSP

Input Parameters

	ksp	- iterative context obtained from KSPCreate
	ell	- number of search directions

Options Database Keys

-ksp_bcgsl_ell ell -

Notes

For large ell it is common for the polynomial update problem to become singular (due to happy breakdown for smallish test problems, but also for larger problems). Consequently, by default, the system is solved by pseudoinverse, which allows the iteration to complete successfully. See KSPBCGSLSetUsePseudoinverse() to switch to a conventional solve.

Keywords