2: #include <petsc/private/snesimpl.h>

  4: /*@
  5:    SNESApplyNPC - Calls SNESSolve() on preconditioner for the SNES

  7:    Collective on SNES

  9:    Input Parameters:
 10: +  snes - the SNES context
 11: .  x - input vector
 12: -  f - optional; the function evaluation on x

 14:    Output Parameter:
 15: .  y - function vector, as set by SNESSetFunction()

 17:    Notes:
 18:    SNESComputeFunction() should be called on x before SNESApplyNPC() is called, as it is
 19:    with SNESComuteJacobian().

 21:    Level: developer

 23: .seealso: SNESGetNPC(),SNESSetNPC(),SNESComputeFunction()
 24: @*/
 25: PetscErrorCode  SNESApplyNPC(SNES snes,Vec x,Vec f,Vec y)
 26: {
 32:   VecValidValues(x,2,PETSC_TRUE);
 33:   if (snes->npc) {
 34:     if (f) {
 35:       SNESSetInitialFunction(snes->npc,f);
 36:     }
 37:     VecCopy(x,y);
 38:     PetscLogEventBegin(SNES_NPCSolve,snes->npc,x,y,0);
 39:     SNESSolve(snes->npc,snes->vec_rhs,y);
 40:     PetscLogEventEnd(SNES_NPCSolve,snes->npc,x,y,0);
 41:     VecAYPX(y,-1.0,x);
 42:     return 0;
 43:   }
 44:   return 0;
 45: }

 47: PetscErrorCode SNESComputeFunctionDefaultNPC(SNES snes,Vec X,Vec F)
 48: {
 49: /* This is to be used as an argument to SNESMF -- NOT as a "function" */
 50:   SNESConvergedReason reason;

 52:   if (snes->npc) {
 53:     SNESApplyNPC(snes,X,NULL,F);
 54:     SNESGetConvergedReason(snes->npc,&reason);
 55:     if (reason < 0  && reason != SNES_DIVERGED_MAX_IT) {
 56:       SNESSetFunctionDomainError(snes);
 57:     }
 58:   } else {
 59:     SNESComputeFunction(snes,X,F);
 60:   }
 61:   return 0;
 62: }

 64: /*@
 65:    SNESGetNPCFunction - Gets the function from a preconditioner after SNESSolve() has been called.

 67:    Collective on SNES

 69:    Input Parameter:
 70: .  snes - the SNES context

 72:    Output Parameters:
 73: +  F - function vector
 74: -  fnorm - the norm of F

 76:    Level: developer

 78: .seealso: SNESGetNPC(),SNESSetNPC(),SNESComputeFunction(),SNESApplyNPC(),SNESSolve()
 79: @*/
 80: PetscErrorCode SNESGetNPCFunction(SNES snes,Vec F,PetscReal *fnorm)
 81: {
 82:   PCSide           npcside;
 83:   SNESFunctionType functype;
 84:   SNESNormSchedule normschedule;
 85:   Vec              FPC,XPC;

 87:   if (snes->npc) {
 88:     SNESGetNPCSide(snes->npc,&npcside);
 89:     SNESGetFunctionType(snes->npc,&functype);
 90:     SNESGetNormSchedule(snes->npc,&normschedule);

 92:     /* check if the function is valid based upon how the inner solver is preconditioned */
 93:     if (normschedule != SNES_NORM_NONE && normschedule != SNES_NORM_INITIAL_ONLY && (npcside == PC_RIGHT || functype == SNES_FUNCTION_UNPRECONDITIONED)) {
 94:       SNESGetFunction(snes->npc,&FPC,NULL,NULL);
 95:       if (FPC) {
 96:         if (fnorm) VecNorm(FPC,NORM_2,fnorm);
 97:         VecCopy(FPC,F);
 98:       } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Preconditioner has no function");
 99:     } else {
100:       SNESGetSolution(snes->npc,&XPC);
101:       if (XPC) {
102:         SNESComputeFunction(snes->npc,XPC,F);
103:         if (fnorm) VecNorm(F,NORM_2,fnorm);
104:       } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Preconditioner has no solution");
105:     }
106:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No preconditioner set");
107:   return 0;
108: }