SNESFAS#

Full Approximation Scheme nonlinear multigrid solver. The nonlinear problem is solved by correction using coarse versions of the nonlinear problem. This problem is perturbed so that a projected solution of the fine problem elicits no correction from the coarse problem.

Options Database Keys and Prefixes#

  • -snes_fas_levels - The number of levels

  • -snes_fas_cycles<1> - The number of cycles – 1 for V, 2 for W

  • -snes_fas_type<additive,multiplicative,full,kaskade> - Additive or multiplicative cycle

  • -snes_fas_galerkin<PETSC_FALSE> - Form coarse problems by projection back upon the fine problem

  • -snes_fas_smoothup<1> - The number of iterations of the post-smoother

  • -snes_fas_smoothdown<1> - The number of iterations of the pre-smoother

  • -snes_fas_monitor - Monitor progress of all of the levels

  • -snes_fas_full_downsweep<PETSC_FALSE> - call the downsmooth on the initial downsweep of full FAS

  • -fas_levels_snes_ - SNES options for all smoothers

  • -fas_levels_cycle_snes_ - SNES options for all cycles

  • -fas_levels_i_snes_ - SNES options for the smoothers on level i

  • -fas_levels_i_cycle_snes_ - SNES options for the cycle on level i

  • -fas_coarse_snes_ - SNES options for the coarsest smoother

Note#

The organization of the FAS solver is slightly different from the organization of PCMG As each level has smoother SNES instances(down and potentially up) and a cycle SNES instance. The cycle SNES instance may be used for monitoring convergence on a particular level.

References#

  • **** -*** Peter R. Brune, Matthew G. Knepley, Barry F. Smith, and Xuemin Tu, “Composing Scalable Nonlinear Algebraic Solvers”, SIAM Review, 57(4), 2015

See Also#

PCMG, SNESCreate(), SNES, SNESSetType(), SNESType, SNESFASSetRestriction(), SNESFASSetInjection(), SNESFASFullGetTotal()

Level#

beginner

Location#

src/snes/impls/fas/fas.c

Edit on GitLab

Index of all SNESFAS routines
Table of Contents for all manual pages
Index of all manual pages