Actual source code: modpcf.c
petsc-3.7.1 2016-05-15
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      2: #include <petsc/private/kspimpl.h>  /*I "petscksp.h" I*/

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

      9:    Logically Collective on KSP

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

     17:    Calling Sequence of function:
     18:     int fcn(KSP ksp,int total_its,int loc_its,PetscReal res_norm,void*ctx);

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

     26:    Options Database Keys:
     27:    -ksp_fgmres_modifypcnochange
     28:    -ksp_fgmres_modifypcksp

     30:    Level: intermediate

     32:    Contributed by Allison Baker

     34:    Notes:
     35:    Several modifypc routines are predefined, including
     36:     KSPFGMRESModifyPCNoChange()
     37:     KSPFGMRESModifyPCKSP()

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

     41: @*/
     42: PetscErrorCode  KSPFGMRESSetModifyPC(KSP ksp,PetscErrorCode (*fcn)(KSP,PetscInt,PetscInt,PetscReal,void*),void *ctx,PetscErrorCode (*d)(void*))
     43: {

     48:   PetscTryMethod(ksp,"KSPFGMRESSetModifyPC_C",(KSP,PetscErrorCode (*)(KSP,PetscInt,PetscInt,PetscReal,void*),void*,PetscErrorCode (*)(void*)),(ksp,fcn,ctx,d));
     49:   return(0);
     50: }

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

     57: /*@

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

     61:   Input Parameters:
     62: +    ksp - the ksp context being used.
     63: .    total_its     - the total number of FGMRES iterations that have occurred.
     64: .    loc_its       - the number of FGMRES iterations since last restart.
     65:                     a restart (so number of Krylov directions to be computed)
     66: .    res_norm      - the current residual norm.
     67: -    dummy         - context variable, unused in this routine

     69:    Level: intermediate

     71:    Contributed by Allison Baker

     73: You can use this as a template!

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

     77: @*/
     78: PetscErrorCode  KSPFGMRESModifyPCNoChange(KSP ksp,PetscInt total_its,PetscInt loc_its,PetscReal res_norm,void *dummy)
     79: {
     81:   return(0);
     82: }

     86: /*@

     88:  KSPFGMRESModifyPCKSP - modifies the attributes of the
     89:      GMRES preconditioner.  It serves as an example (not as something
     90:      useful!)

     92:   Input Parameters:
     93: +    ksp - the ksp context being used.
     94: .    total_its     - the total number of FGMRES iterations that have occurred.
     95: .    loc_its       - the number of FGMRES iterations since last restart.
     96: .    res_norm      - the current residual norm.
     97: -    dummy         - context, not used here

     99:    Level: intermediate

    101:    Contributed by Allison Baker

    103:  This could be used as a template!

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

    107: @*/
    108: PetscErrorCode  KSPFGMRESModifyPCKSP(KSP ksp,PetscInt total_its,PetscInt loc_its,PetscReal res_norm,void *dummy)
    109: {
    110:   PC             pc;
    112:   PetscInt       maxits;
    113:   KSP            sub_ksp;
    114:   PetscReal      rtol,abstol,dtol;
    115:   PetscBool      isksp;

    118:   KSPGetPC(ksp,&pc);

    120:   PetscObjectTypeCompare((PetscObject)pc,PCKSP,&isksp);
    121:   if (isksp) {
    122:     PCKSPGetKSP(pc,&sub_ksp);

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

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

    129:     KSPGetTolerances(sub_ksp,&rtol,&abstol,&dtol,&maxits);
    130:     if (!loc_its) rtol = .1;
    131:     else rtol *= .9;
    132:     KSPSetTolerances(sub_ksp,rtol,abstol,dtol,maxits);
    133:   }
    134:   return(0);
    135: }