/* $Id: modpcf.c,v 1.14 2001/04/10 19:36:35 bsmith Exp $*/

#include "petscsles.h" 
#undef __FUNCT__  
#define __FUNCT__ "KSPFGMRESSetModifyPC"
/*@C
   KSPFGMRESSetModifyPC - Sets the routine used by FGMRES to modify the preconditioner.

   Collective on KSP

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

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

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

   Options Database Keys:
   -ksp_fgmres_modifypcnochange
   -ksp_fgmres_modifypcsles

   Level: intermediate

   Contributed by Allison Baker

   Notes:
   Several modifypc routines are predefined, including
    KSPFGMRESModifyPCNoChange()
    KSPFGMRESModifyPCSLES()

.seealso: KSPFGMRESModifyPCNoChange(), KSPFGMRESModifyPCSLES()

@*/
int KSPFGMRESSetModifyPC(KSP ksp,int (*fcn)(KSP,int,int,PetscReal,void*),void* ctx,int (*d)(void*))
{
  int ierr,(*f)(KSP,int (*)(KSP,int,int,PetscReal,void*),void*,int (*)(void*));

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ksp,KSP_COOKIE);
  ierr = PetscObjectQueryFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",(void (**)(void))&f);CHKERRQ(ierr);
  if (f) {
    ierr = (*f)(ksp,fcn,ctx,d);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}



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

#undef __FUNCT__  
#define __FUNCT__ "KSPFGMRESModifyPCNoChange"
/*@C

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

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

   Level: intermediate

   Contributed by Allison Baker

You can use this as a template!

.seealso: KSPFGMRESSetModifyPC(), KSPFGMRESModifyPCSLES()

@*/
int KSPFGMRESModifyPCNoChange(KSP ksp,int total_its,int loc_its,PetscReal res_norm,void* dummy)
{
  PetscFunctionBegin;

  PetscFunctionReturn(0);
}

#undef __FUNCT__  
#define __FUNCT__ "KSPFGMRESModifyPCSLES"
/*@C

 KSPFGMRESModifyPCSLES - modifies the attributes of the
     GMRES preconditioner.  It serves as an example (not as something 
     useful!) 

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

   Level: intermediate

   Contributed by Allison Baker

 This could be used as a template!

.seealso: KSPFGMRESSetModifyPC(), KSPFGMRESModifyPCSLES()

@*/
int KSPFGMRESModifyPCSLES(KSP ksp,int total_its,int loc_its,PetscReal res_norm,void *dummy)
{
  PC         pc;
  int        ierr,maxits;
  SLES       sub_sles;
  KSP        sub_ksp;
  PetscReal  rtol,atol,dtol;
  PetscTruth issles;

  PetscFunctionBegin;

  ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);

  ierr = PetscTypeCompare((PetscObject)pc,PCSLES,&issles);CHKERRQ(ierr);
  if (issles) { 
    ierr = PCSLESGetSLES(pc,&sub_sles);CHKERRQ(ierr);
    ierr = SLESGetKSP(sub_sles,&sub_ksp);CHKERRQ(ierr);
  
    /* note that at this point you could check the type of KSP with KSPGetType() */  

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

    ierr = KSPGetTolerances(sub_ksp,&rtol,&atol,&dtol,&maxits);CHKERRQ(ierr);
    if (loc_its == 0) {
      rtol = .1;
    } else {
      rtol *= .9;
    }
    ierr = KSPSetTolerances(sub_ksp,rtol,atol,dtol,maxits);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}