xref: /petsc/src/ksp/pc/impls/sor/sor.c (revision 2fa5cd679192b9b390e47ae2d0650965e6b1d9fa)

/*
   Defines a  (S)SOR  preconditioner for any Mat implementation
*/
#include <petsc-private/pcimpl.h>               /*I "petscpc.h" I*/

typedef struct {
  PetscInt   its;         /* inner iterations, number of sweeps */
  PetscInt   lits;        /* local inner iterations, number of sweeps applied by the local matrix mat->A */
  MatSORType sym;         /* forward, reverse, symmetric etc. */
  PetscReal  omega;
  PetscReal  fshift;
} PC_SOR;

#undef __FUNCT__
#define __FUNCT__ "PCDestroy_SOR"
static PetscErrorCode PCDestroy_SOR(PC pc)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscFree(pc->data);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "PCApply_SOR"
static PetscErrorCode PCApply_SOR(PC pc,Vec x,Vec y)
{
  PC_SOR         *jac = (PC_SOR*)pc->data;
  PetscErrorCode ierr;
  PetscInt       flag = jac->sym | SOR_ZERO_INITIAL_GUESS;

  PetscFunctionBegin;
  ierr = MatSOR(pc->pmat,x,jac->omega,(MatSORType)flag,jac->fshift,jac->its,jac->lits,y);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "PCApplyRichardson_SOR"
static PetscErrorCode PCApplyRichardson_SOR(PC pc,Vec b,Vec y,Vec w,PetscReal rtol,PetscReal abstol, PetscReal dtol,PetscInt its,PetscBool guesszero,PetscInt *outits,PCRichardsonConvergedReason *reason)
{
  PC_SOR         *jac = (PC_SOR*)pc->data;
  PetscErrorCode ierr;
  MatSORType     stype = jac->sym;

  PetscFunctionBegin;
  ierr = PetscInfo1(pc,"Warning, convergence critera ignored, using %D iterations\n",its);CHKERRQ(ierr);
  if (guesszero) stype = (MatSORType) (stype | SOR_ZERO_INITIAL_GUESS);
  ierr = MatSOR(pc->pmat,b,jac->omega,stype,jac->fshift,its*jac->its,jac->lits,y);CHKERRQ(ierr);
  *outits = its;
  *reason = PCRICHARDSON_CONVERGED_ITS;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "PCSetFromOptions_SOR"
PetscErrorCode PCSetFromOptions_SOR(PC pc)
{
  PC_SOR         *jac = (PC_SOR*)pc->data;
  PetscErrorCode ierr;
  PetscBool      flg;

  PetscFunctionBegin;
  ierr = PetscOptionsHead("(S)SOR options");CHKERRQ(ierr);
  ierr = PetscOptionsReal("-pc_sor_omega","relaxation factor (0 < omega < 2)","PCSORSetOmega",jac->omega,&jac->omega,0);CHKERRQ(ierr);
  ierr = PetscOptionsReal("-pc_sor_diagonal_shift","Add to the diagonal entries","",jac->fshift,&jac->fshift,0);CHKERRQ(ierr);
  ierr = PetscOptionsInt("-pc_sor_its","number of inner SOR iterations","PCSORSetIterations",jac->its,&jac->its,0);CHKERRQ(ierr);
  ierr = PetscOptionsInt("-pc_sor_lits","number of local inner SOR iterations","PCSORSetIterations",jac->lits,&jac->lits,0);CHKERRQ(ierr);
  ierr = PetscOptionsBoolGroupBegin("-pc_sor_symmetric","SSOR, not SOR","PCSORSetSymmetric",&flg);CHKERRQ(ierr);
  if (flg) {ierr = PCSORSetSymmetric(pc,SOR_SYMMETRIC_SWEEP);CHKERRQ(ierr);}
  ierr = PetscOptionsBoolGroup("-pc_sor_backward","use backward sweep instead of forward","PCSORSetSymmetric",&flg);CHKERRQ(ierr);
  if (flg) {ierr = PCSORSetSymmetric(pc,SOR_BACKWARD_SWEEP);CHKERRQ(ierr);}
  ierr = PetscOptionsBoolGroup("-pc_sor_forward","use forward sweep","PCSORSetSymmetric",&flg);CHKERRQ(ierr);
  if (flg) {ierr = PCSORSetSymmetric(pc,SOR_FORWARD_SWEEP);CHKERRQ(ierr);}
  ierr = PetscOptionsBoolGroup("-pc_sor_local_symmetric","use SSOR separately on each processor","PCSORSetSymmetric",&flg);CHKERRQ(ierr);
  if (flg) {ierr = PCSORSetSymmetric(pc,SOR_LOCAL_SYMMETRIC_SWEEP);CHKERRQ(ierr);}
  ierr = PetscOptionsBoolGroup("-pc_sor_local_backward","use backward sweep locally","PCSORSetSymmetric",&flg);CHKERRQ(ierr);
  if (flg) {ierr = PCSORSetSymmetric(pc,SOR_LOCAL_BACKWARD_SWEEP);CHKERRQ(ierr);}
  ierr = PetscOptionsBoolGroupEnd("-pc_sor_local_forward","use forward sweep locally","PCSORSetSymmetric",&flg);CHKERRQ(ierr);
  if (flg) {ierr = PCSORSetSymmetric(pc,SOR_LOCAL_FORWARD_SWEEP);CHKERRQ(ierr);}
  ierr = PetscOptionsTail();CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "PCView_SOR"
PetscErrorCode PCView_SOR(PC pc,PetscViewer viewer)
{
  PC_SOR         *jac = (PC_SOR*)pc->data;
  MatSORType     sym  = jac->sym;
  const char     *sortype;
  PetscErrorCode ierr;
  PetscBool      iascii;

  PetscFunctionBegin;
  ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
  if (iascii) {
    if (sym & SOR_ZERO_INITIAL_GUESS) {ierr = PetscViewerASCIIPrintf(viewer,"  SOR:  zero initial guess\n");CHKERRQ(ierr);}
    if (sym == SOR_APPLY_UPPER)                                              sortype = "apply_upper";
    else if (sym == SOR_APPLY_LOWER)                                         sortype = "apply_lower";
    else if (sym & SOR_EISENSTAT)                                            sortype = "Eisenstat";
    else if ((sym & SOR_SYMMETRIC_SWEEP) == SOR_SYMMETRIC_SWEEP)             sortype = "symmetric";
    else if (sym & SOR_BACKWARD_SWEEP)                                       sortype = "backward";
    else if (sym & SOR_FORWARD_SWEEP)                                        sortype = "forward";
    else if ((sym & SOR_LOCAL_SYMMETRIC_SWEEP) == SOR_LOCAL_SYMMETRIC_SWEEP) sortype = "local_symmetric";
    else if (sym & SOR_LOCAL_FORWARD_SWEEP)                                  sortype = "local_forward";
    else if (sym & SOR_LOCAL_BACKWARD_SWEEP)                                 sortype = "local_backward";
    else                                                                     sortype = "unknown";
    ierr = PetscViewerASCIIPrintf(viewer,"  SOR: type = %s, iterations = %D, local iterations = %D, omega = %G\n",sortype,jac->its,jac->lits,jac->omega);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}


/* ------------------------------------------------------------------------------*/
EXTERN_C_BEGIN
#undef __FUNCT__
#define __FUNCT__ "PCSORSetSymmetric_SOR"
PetscErrorCode  PCSORSetSymmetric_SOR(PC pc,MatSORType flag)
{
  PC_SOR *jac;

  PetscFunctionBegin;
  jac      = (PC_SOR*)pc->data;
  jac->sym = flag;
  PetscFunctionReturn(0);
}
EXTERN_C_END

EXTERN_C_BEGIN
#undef __FUNCT__
#define __FUNCT__ "PCSORSetOmega_SOR"
PetscErrorCode  PCSORSetOmega_SOR(PC pc,PetscReal omega)
{
  PC_SOR *jac;

  PetscFunctionBegin;
  if (omega >= 2.0 || omega <= 0.0) SETERRQ(((PetscObject)pc)->comm,PETSC_ERR_ARG_OUTOFRANGE,"Relaxation out of range");
  jac        = (PC_SOR*)pc->data;
  jac->omega = omega;
  PetscFunctionReturn(0);
}
EXTERN_C_END

EXTERN_C_BEGIN
#undef __FUNCT__
#define __FUNCT__ "PCSORSetIterations_SOR"
PetscErrorCode  PCSORSetIterations_SOR(PC pc,PetscInt its,PetscInt lits)
{
  PC_SOR *jac;

  PetscFunctionBegin;
  jac       = (PC_SOR*)pc->data;
  jac->its  = its;
  jac->lits = lits;
  PetscFunctionReturn(0);
}
EXTERN_C_END

/* ------------------------------------------------------------------------------*/
#undef __FUNCT__
#define __FUNCT__ "PCSORSetSymmetric"
/*@
   PCSORSetSymmetric - Sets the SOR preconditioner to use symmetric (SSOR),
   backward, or forward relaxation.  The local variants perform SOR on
   each processor.  By default forward relaxation is used.

   Logically Collective on PC

   Input Parameters:
+  pc - the preconditioner context
-  flag - one of the following
.vb
    SOR_FORWARD_SWEEP
    SOR_BACKWARD_SWEEP
    SOR_SYMMETRIC_SWEEP
    SOR_LOCAL_FORWARD_SWEEP
    SOR_LOCAL_BACKWARD_SWEEP
    SOR_LOCAL_SYMMETRIC_SWEEP
.ve

   Options Database Keys:
+  -pc_sor_symmetric - Activates symmetric version
.  -pc_sor_backward - Activates backward version
.  -pc_sor_local_forward - Activates local forward version
.  -pc_sor_local_symmetric - Activates local symmetric version
-  -pc_sor_local_backward - Activates local backward version

   Notes:
   To use the Eisenstat trick with SSOR, employ the PCEISENSTAT preconditioner,
   which can be chosen with the option
.  -pc_type eisenstat - Activates Eisenstat trick

   Level: intermediate

.keywords: PC, SOR, SSOR, set, relaxation, sweep, forward, backward, symmetric

.seealso: PCEisenstatSetOmega(), PCSORSetIterations(), PCSORSetOmega()
@*/
PetscErrorCode  PCSORSetSymmetric(PC pc,MatSORType flag)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc,PC_CLASSID,1);
  PetscValidLogicalCollectiveEnum(pc,flag,2);
  ierr = PetscTryMethod(pc,"PCSORSetSymmetric_C",(PC,MatSORType),(pc,flag));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "PCSORSetOmega"
/*@
   PCSORSetOmega - Sets the SOR relaxation coefficient, omega
   (where omega = 1.0 by default).

   Logically Collective on PC

   Input Parameters:
+  pc - the preconditioner context
-  omega - relaxation coefficient (0 < omega < 2).

   Options Database Key:
.  -pc_sor_omega <omega> - Sets omega

   Level: intermediate

.keywords: PC, SOR, SSOR, set, relaxation, omega

.seealso: PCSORSetSymmetric(), PCSORSetIterations(), PCEisenstatSetOmega()
@*/
PetscErrorCode  PCSORSetOmega(PC pc,PetscReal omega)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc,PC_CLASSID,1);
  PetscValidLogicalCollectiveReal(pc,omega,2);
  ierr = PetscTryMethod(pc,"PCSORSetOmega_C",(PC,PetscReal),(pc,omega));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "PCSORSetIterations"
/*@
   PCSORSetIterations - Sets the number of inner iterations to
   be used by the SOR preconditioner. The default is 1.

   Logically Collective on PC

   Input Parameters:
+  pc - the preconditioner context
.  lits - number of local iterations, smoothings over just variables on processor
-  its - number of parallel iterations to use; each parallel iteration has lits local iterations

   Options Database Key:
+  -pc_sor_its <its> - Sets number of iterations
-  -pc_sor_lits <lits> - Sets number of local iterations

   Level: intermediate

   Notes: When run on one processor the number of smoothings is lits*its

.keywords: PC, SOR, SSOR, set, iterations

.seealso: PCSORSetOmega(), PCSORSetSymmetric()
@*/
PetscErrorCode  PCSORSetIterations(PC pc,PetscInt its,PetscInt lits)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc,PC_CLASSID,1);
  PetscValidLogicalCollectiveInt(pc,its,2);
  ierr = PetscTryMethod(pc,"PCSORSetIterations_C",(PC,PetscInt,PetscInt),(pc,its,lits));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*MC
     PCSOR - (S)SOR (successive over relaxation, Gauss-Seidel) preconditioning

   Options Database Keys:
+  -pc_sor_symmetric - Activates symmetric version
.  -pc_sor_backward - Activates backward version
.  -pc_sor_forward - Activates forward version
.  -pc_sor_local_forward - Activates local forward version
.  -pc_sor_local_symmetric - Activates local symmetric version  (default version)
.  -pc_sor_local_backward - Activates local backward version
.  -pc_sor_omega <omega> - Sets omega
.  -pc_sor_its <its> - Sets number of iterations   (default 1)
-  -pc_sor_lits <lits> - Sets number of local iterations  (default 1)

   Level: beginner

  Concepts: SOR, preconditioners, Gauss-Seidel

   Notes: Only implemented for the AIJ  and SeqBAIJ matrix formats.
          Not a true parallel SOR, in parallel this implementation corresponds to block
          Jacobi with SOR on each block.

          For SeqBAIJ matrices this implements point-block SOR, but the omega, its, lits options are not supported.

.seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PC,
           PCSORSetIterations(), PCSORSetSymmetric(), PCSORSetOmega(), PCEISENSTAT
M*/

EXTERN_C_BEGIN
#undef __FUNCT__
#define __FUNCT__ "PCCreate_SOR"
PetscErrorCode  PCCreate_SOR(PC pc)
{
  PetscErrorCode ierr;
  PC_SOR         *jac;

  PetscFunctionBegin;
  ierr = PetscNewLog(pc,PC_SOR,&jac);CHKERRQ(ierr);

  pc->ops->apply           = PCApply_SOR;
  pc->ops->applyrichardson = PCApplyRichardson_SOR;
  pc->ops->setfromoptions  = PCSetFromOptions_SOR;
  pc->ops->setup           = 0;
  pc->ops->view            = PCView_SOR;
  pc->ops->destroy         = PCDestroy_SOR;
  pc->data                 = (void*)jac;
  jac->sym                 = SOR_LOCAL_SYMMETRIC_SWEEP;
  jac->omega               = 1.0;
  jac->fshift              = 0.0;
  jac->its                 = 1;
  jac->lits                = 1;

  ierr = PetscObjectComposeFunctionDynamic((PetscObject)pc,"PCSORSetSymmetric_C","PCSORSetSymmetric_SOR",
                                           PCSORSetSymmetric_SOR);CHKERRQ(ierr);
  ierr = PetscObjectComposeFunctionDynamic((PetscObject)pc,"PCSORSetOmega_C","PCSORSetOmega_SOR",
                                           PCSORSetOmega_SOR);CHKERRQ(ierr);
  ierr = PetscObjectComposeFunctionDynamic((PetscObject)pc,"PCSORSetIterations_C","PCSORSetIterations_SOR",
                                           PCSORSetIterations_SOR);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}
EXTERN_C_END