Actual source code: fasgalerkin.c

petsc-master 2020-09-18
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  1: #include <../src/snes/impls/fas/fasimpls.h>

  3: /*@
  4:    SNESFASGetGalerkin - Gets if the coarse problems are formed by projection to the fine problem

  6:    Input Parameter:
  7: .  snes - the nonlinear solver context

  9:    Output parameter:
 10: .  flg - the status of the galerkin problem

 12:    Level: advanced

 14: .seealso: SNESFASSetLevels(), SNESFASSetGalerkin()
 15: @*/
 16: PetscErrorCode SNESFASGetGalerkin(SNES snes, PetscBool *flg)
 17: {
 18:   SNES_FAS *fas;

 22:   fas = (SNES_FAS*)snes->data;
 23:   *flg = fas->galerkin;
 24:   return(0);
 25: }

 27: /*@
 28:    SNESFASSetGalerkin - Sets coarse problems as formed by projection to the fine problem

 30:    Input Parameter:
 31: +  snes - the nonlinear solver context
 32: -  flg - the status of the galerkin problem

 34:    Level: advanced

 36: .seealso: SNESFASSetLevels(), SNESFASGetGalerkin()
 37: @*/
 38: PetscErrorCode SNESFASSetGalerkin(SNES snes, PetscBool flg)
 39: {
 40:   SNES_FAS       *fas;

 45:   fas = (SNES_FAS*)snes->data;
 46:   fas->galerkin = flg;
 47:   if (fas->next) {SNESFASSetGalerkin(fas->next, flg);}
 48:   return(0);
 49: }

 51: /*@C
 52:    SNESFASGalerkinFunctionDefault - Computes the Galerkin FAS function

 54:    Input Parameters:
 55: +  snes - the nonlinear solver context
 56: .  X - input vector
 57: -  ctx - the FAS context

 59:    Output Parameter:
 60: .  F - output vector

 62:    Notes:
 63:    The Galerkin FAS function evalutation is defined as
 64: $  F^l(x^l) = I^l_0 F^0(P^0_l x^l)

 66:    Level: developer

 68: .seealso: SNESFASGetGalerkin(), SNESFASSetGalerkin()
 69: @*/
 70: PetscErrorCode SNESFASGalerkinFunctionDefault(SNES snes, Vec X, Vec F, void *ctx)
 71: {
 72:   SNES           fassnes;
 73:   SNES_FAS       *fas;
 74:   SNES_FAS       *prevfas;
 75:   SNES           prevsnes;
 76:   Vec            b_temp;

 80:   /* prolong to the fine level and evaluate there. */
 81:   fassnes  = (SNES)ctx;
 82:   fas      = (SNES_FAS*)fassnes->data;
 83:   prevsnes = fas->previous;
 84:   prevfas  = (SNES_FAS*)prevsnes->data;
 85:   /* interpolate down the solution */
 86:   MatInterpolate(prevfas->interpolate, X, prevfas->Xg);
 87:   /* the RHS we care about is at the coarsest level */
 88:   b_temp            = prevsnes->vec_rhs;
 89:   prevsnes->vec_rhs = NULL;
 90:   SNESComputeFunction(prevsnes, prevfas->Xg, prevfas->Fg);
 91:   prevsnes->vec_rhs = b_temp;
 92:   /* restrict up the function */
 93:   MatRestrict(prevfas->restrct, prevfas->Fg, F);
 94:   return(0);
 95: }