KSPBCGSLSetEll

Sets the number of search directions to use in the KSPCBGSL solver

Synopsis

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

Logically Collective

Input Parameters

• ksp - iterative context of type KSPCBGSL

• ell - number of search directions

Options Database Key

• -ksp_bcgsl_ell ell - Number of Krylov search directions

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.

See Also

KSP: Linear System Solvers, KSPBCGSLSetUsePseudoinverse(), KSP, KSPBCGSL, KSPBCGSLSetPol(), KSPBCGSLSetXRes()

Level

intermediate

Location

src/ksp/ksp/impls/bcgsl/bcgsl.c

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