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: {

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

 50: PetscErrorCode SNESComputeFunctionDefaultNPC(SNES snes,Vec X,Vec F)
 51: {
 52: /* This is to be used as an argument to SNESMF -- NOT as a "function" */
 53:   SNESConvergedReason reason;
 54:   PetscErrorCode      ierr;

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

 69: /*@
 70:    SNESGetNPCFunction - Gets the function from a preconditioner after SNESSolve() has been called.

 72:    Collective on SNES

 74:    Input Parameters:
 75: .  snes - the SNES context

 77:    Output Parameter:
 78: +  F - function vector
 79: -  fnorm - the norm of F

 81:    Level: developer

 83: .seealso: SNESGetNPC(),SNESSetNPC(),SNESComputeFunction(),SNESApplyNPC(),SNESSolve()
 84: @*/
 85: PetscErrorCode SNESGetNPCFunction(SNES snes,Vec F,PetscReal *fnorm)
 86: {
 87:   PetscErrorCode   ierr;
 88:   PCSide           npcside;
 89:   SNESFunctionType functype;
 90:   SNESNormSchedule normschedule;
 91:   Vec              FPC,XPC;

 94:   if (snes->npc) {
 95:     SNESGetNPCSide(snes->npc,&npcside);
 96:     SNESGetFunctionType(snes->npc,&functype);
 97:     SNESGetNormSchedule(snes->npc,&normschedule);

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