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: .keywords: SNES, nonlinear, compute, function

 25: .seealso: SNESGetNPC(),SNESSetNPC(),SNESComputeFunction()
 26: @*/
 27: PetscErrorCode  SNESApplyNPC(SNES snes,Vec x,Vec f,Vec y)
 28: {

 37:   VecValidValues(x,2,PETSC_TRUE);
 38:   if (snes->npc) {
 39:     if (f) {
 40:       SNESSetInitialFunction(snes->npc,f);
 41:     }
 42:     VecCopy(x,y);
 43:     PetscLogEventBegin(SNES_NPCSolve,snes->npc,x,y,0);
 44:     SNESSolve(snes->npc,snes->vec_rhs,y);
 45:     PetscLogEventEnd(SNES_NPCSolve,snes->npc,x,y,0);
 46:     VecAYPX(y,-1.0,x);
 47:     return(0);
 48:   }
 49:   return(0);
 50: }

 52: PetscErrorCode SNESComputeFunctionDefaultNPC(SNES snes,Vec X,Vec F)
 53: {
 54: /* This is to be used as an argument to SNESMF -- NOT as a "function" */
 55:   SNESConvergedReason reason;
 56:   PetscErrorCode      ierr;

 59:   if (snes->npc) {
 60:     SNESApplyNPC(snes,X,NULL,F);
 61:     SNESGetConvergedReason(snes->npc,&reason);
 62:     if (reason < 0  && reason != SNES_DIVERGED_MAX_IT) {
 63:       SNESSetFunctionDomainError(snes);
 64:     }
 65:   } else {
 66:     SNESComputeFunction(snes,X,F);
 67:   }
 68:   return(0);
 69: }

 71: /*@
 72:    SNESGetNPCFunction - Gets the function from a preconditioner after SNESSolve() has been called.

 74:    Collective on SNES

 76:    Input Parameters:
 77: .  snes - the SNES context

 79:    Output Parameter:
 80: .  F - function vector
 81: .  fnorm - the norm of F

 83:    Level: developer

 85: .keywords: SNES, nonlinear, function

 87: .seealso: SNESGetNPC(),SNESSetNPC(),SNESComputeFunction(),SNESApplyNPC(),SNESSolve()
 88: @*/
 89: PetscErrorCode SNESGetNPCFunction(SNES snes,Vec F,PetscReal *fnorm)
 90: {
 91:   PetscErrorCode   ierr;
 92:   PCSide           npcside;
 93:   SNESFunctionType functype;
 94:   SNESNormSchedule normschedule;
 95:   Vec              FPC,XPC;

 98:   if (snes->npc) {
 99:     SNESGetNPCSide(snes->npc,&npcside);
100:     SNESGetFunctionType(snes->npc,&functype);
101:     SNESGetNormSchedule(snes->npc,&normschedule);

103:     /* check if the function is valid based upon how the inner solver is preconditioned */
104:     if (normschedule != SNES_NORM_NONE && normschedule != SNES_NORM_INITIAL_ONLY && (npcside == PC_RIGHT || functype == SNES_FUNCTION_UNPRECONDITIONED)) {
105:       SNESGetFunction(snes->npc,&FPC,NULL,NULL);
106:       if (FPC) {
107:         if (fnorm) {VecNorm(FPC,NORM_2,fnorm);}
108:         VecCopy(FPC,F);
109:       } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Preconditioner has no function");
110:     } else {
111:       SNESGetSolution(snes->npc,&XPC);
112:       if (XPC) {
113:         SNESComputeFunction(snes->npc,XPC,F);
114:         if (fnorm) {VecNorm(F,NORM_2,fnorm);}
115:       } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Preconditioner has no solution");
116:     }
117:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No preconditioner set");
118:   return(0);
119: }