Actual source code: snespc.c
petsc-3.13.6 2020-09-29
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      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: }