SNESGetLagPreconditioner#

Return how often the preconditioner is rebuilt

Synopsis#

#include "petscsnes.h"  
PetscErrorCode SNESGetLagPreconditioner(SNES snes, PetscInt *lag)

Not Collective

Input Parameter#

  • snes - the SNES context

Output Parameter#

  • lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

Options Database Keys#

  • -snes_lag_jacobian_persists <true,false> - sets the persistence through multiple SNES solves

  • -snes_lag_jacobian <- 2,1,2,…> - sets the lag

  • -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves

  • -snes_lag_preconditioner <- 2,1,2,…> - sets the lag

Notes#

The default is 1

The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

See Also#

SNES: Nonlinear Solvers, SNES, SNESSetTrustRegionTolerance(), SNESSetLagPreconditioner(), SNESSetLagJacobianPersists(), SNESSetLagPreconditionerPersists()

Level#

intermediate

Location#

src/snes/interface/snes.c

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Index of all SNES routines
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Index of all manual pages