Date: 2022-03-31T04:48:10+00:00

Actual source code: modpcf.c

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

      4: /*@C
      5:    KSPFGMRESSetModifyPC - Sets the routine used by FGMRES to modify the preconditioner.

      7:    Logically Collective on ksp

      9:    Input Parameters:
     10: +  ksp - iterative context obtained from KSPCreate
     11: .  fcn - modifypc function
     12: .  ctx - optional context
     13: -  d - optional context destroy routine

     15:    Calling Sequence of function:
     16:     PetscErrorCode fcn(KSP ksp,PetscInt total_its,PetscInt loc_its,PetscReal res_norm,void*ctx);

     18:     ksp - the ksp context being used.
     19:     total_its     - the total number of FGMRES iterations that have occurred.
     20:     loc_its       - the number of FGMRES iterations since last restart.
     21:     res_norm      - the current residual norm.
     22:     ctx           - optional context variable

     24:    Options Database Keys:
     25:    -ksp_fgmres_modifypcnochange
     26:    -ksp_fgmres_modifypcksp

     28:    Level: intermediate

     30:    Contributed by Allison Baker

     32:    Notes:
     33:    Several modifypc routines are predefined, including
     34:     KSPFGMRESModifyPCNoChange()
     35:     KSPFGMRESModifyPCKSP()

     37: .seealso: KSPFGMRESModifyPCNoChange(), KSPFGMRESModifyPCKSP()

     39: @*/
     40: PetscErrorCode  KSPFGMRESSetModifyPC(KSP ksp,PetscErrorCode (*fcn)(KSP,PetscInt,PetscInt,PetscReal,void*),void *ctx,PetscErrorCode (*d)(void*))
     41: {
     43:   PetscTryMethod(ksp,"KSPFGMRESSetModifyPC_C",(KSP,PetscErrorCode (*)(KSP,PetscInt,PetscInt,PetscReal,void*),void*,PetscErrorCode (*)(void*)),(ksp,fcn,ctx,d));
     44:   return 0;
     45: }

     47: /* The following are different routines used to modify the preconditioner */

     49: /*@

     51:   KSPFGMRESModifyPCNoChange - this is the default used by fgmres - it doesn't change the preconditioner.

     53:   Input Parameters:
     54: +    ksp - the ksp context being used.
     55: .    total_its     - the total number of FGMRES iterations that have occurred.
     56: .    loc_its       - the number of FGMRES iterations since last restart.
     57:                     a restart (so number of Krylov directions to be computed)
     58: .    res_norm      - the current residual norm.
     59: -    dummy         - context variable, unused in this routine

     61:    Level: intermediate

     63:    Contributed by Allison Baker

     65: You can use this as a template!

     67: .seealso: KSPFGMRESSetModifyPC(), KSPFGMRESModifyPCKSP()

     69: @*/
     70: PetscErrorCode  KSPFGMRESModifyPCNoChange(KSP ksp,PetscInt total_its,PetscInt loc_its,PetscReal res_norm,void *dummy)
     71: {
     72:   return 0;
     73: }

     75: /*@

     77:  KSPFGMRESModifyPCKSP - modifies the attributes of the
     78:      GMRES preconditioner.  It serves as an example (not as something
     79:      useful!)

     81:   Input Parameters:
     82: +    ksp - the ksp context being used.
     83: .    total_its     - the total number of FGMRES iterations that have occurred.
     84: .    loc_its       - the number of FGMRES iterations since last restart.
     85: .    res_norm      - the current residual norm.
     86: -    dummy         - context, not used here

     88:    Level: intermediate

     90:    Contributed by Allison Baker

     92:  This could be used as a template!

     94: .seealso: KSPFGMRESSetModifyPC(), KSPFGMRESModifyPCKSP()

     96: @*/
     97: PetscErrorCode  KSPFGMRESModifyPCKSP(KSP ksp,PetscInt total_its,PetscInt loc_its,PetscReal res_norm,void *dummy)
     98: {
     99:   PC             pc;
    100:   PetscInt       maxits;
    101:   KSP            sub_ksp;
    102:   PetscReal      rtol,abstol,dtol;
    103:   PetscBool      isksp;

    105:   KSPGetPC(ksp,&pc);

    107:   PetscObjectTypeCompare((PetscObject)pc,PCKSP,&isksp);
    108:   if (isksp) {
    109:     PCKSPGetKSP(pc,&sub_ksp);

    111:     /* note that at this point you could check the type of KSP with KSPGetType() */

    113:     /* Now we can use functions such as KSPGMRESSetRestart() or
    114:       KSPGMRESSetOrthogonalization() or KSPSetTolerances() */

    116:     KSPGetTolerances(sub_ksp,&rtol,&abstol,&dtol,&maxits);
    117:     if (!loc_its) rtol = .1;
    118:     else rtol *= .9;
    119:     KSPSetTolerances(sub_ksp,rtol,abstol,dtol,maxits);
    120:   }
    121:   return 0;
    122: }