Actual source code: modpcf.c

petsc-3.5.2 2014-09-08
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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: }