Date: 2013-07-02T14:47:54+00:00

Actual source code: itres.c
petsc-3.4.2 2013-07-02

      2: #include <petsc-private/kspimpl.h>   /*I "petscksp.h" I*/

      6: /*@
      7:    KSPInitialResidual - Computes the residual. Either b - A*C*u = b - A*x with right
      8:      preconditioning or C*(b - A*x) with left preconditioning; that later
      9:      residual is often called the "preconditioned residual".

     11:    Collective on KSP

     13:    Input Parameters:
     14: +  vsoln    - solution to use in computing residual
     15: .  vt1, vt2 - temporary work vectors
     16: -  vb       - right-hand-side vector

     18:    Output Parameters:
     19: .  vres     - calculated residual

     21:    Notes:
     22:    This routine assumes that an iterative method, designed for
     23: $     A x = b
     24:    will be used with a preconditioner, C, such that the actual problem is either
     25: $     AC u = b (right preconditioning) or
     26: $     CA x = Cb (left preconditioning).
     27:    This means that the calculated residual will be scaled and/or preconditioned;
     28:    the true residual
     29: $     b-Ax
     30:    is returned in the vt2 temporary.

     32:    Level: developer

     34: .keywords: KSP, residual

     36: .seealso:  KSPMonitor()
     37: @*/

     39: PetscErrorCode  KSPInitialResidual(KSP ksp,Vec vsoln,Vec vt1,Vec vt2,Vec vres,Vec vb)
     40: {
     41:   MatStructure   pflag;
     42:   Mat            Amat,Pmat;

     50:   if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
     51:   PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);
     52:   if (!ksp->guess_zero) {
     53:     /* skip right scaling since current guess already has it */
     54:     KSP_MatMult(ksp,Amat,vsoln,vt1);
     55:     VecCopy(vb,vt2);
     56:     VecAXPY(vt2,-1.0,vt1);
     57:     (ksp->pc_side == PC_RIGHT) ? (VecCopy(vt2,vres)) : (KSP_PCApply(ksp,vt2,vres));
     58:     PCDiagonalScaleLeft(ksp->pc,vres,vres);
     59:   } else {
     60:     VecCopy(vb,vt2);
     61:     if (ksp->pc_side == PC_RIGHT) {
     62:       PCDiagonalScaleLeft(ksp->pc,vb,vres);
     63:     } else if (ksp->pc_side == PC_LEFT) {
     64:       KSP_PCApply(ksp,vb,vres);
     65:       PCDiagonalScaleLeft(ksp->pc,vres,vres);
     66:     } else if (ksp->pc_side == PC_SYMMETRIC) {
     67:       PCApplySymmetricLeft(ksp->pc, vb, vres);
     68:     } else SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP, "Invalid preconditioning side %d", (int)ksp->pc_side);
     69:   }
     70:   return(0);
     71: }

     75: /*@
     76:    KSPUnwindPreconditioner - Unwinds the preconditioning in the solution. That is,
     77:      takes solution to the preconditioned problem and gets the solution to the
     78:      original problem from it.

     80:    Collective on KSP

     82:    Input Parameters:
     83: +  ksp  - iterative context
     84: .  vsoln - solution vector
     85: -  vt1   - temporary work vector

     87:    Output Parameter:
     88: .  vsoln - contains solution on output

     90:    Notes:
     91:    If preconditioning either symmetrically or on the right, this routine solves
     92:    for the correction to the unpreconditioned problem.  If preconditioning on
     93:    the left, nothing is done.

     95:    Level: advanced

     97: .keywords: KSP, unwind, preconditioner

     99: .seealso: KSPSetPCSide()
    100: @*/
    101: PetscErrorCode  KSPUnwindPreconditioner(KSP ksp,Vec vsoln,Vec vt1)
    102: {

    108:   if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
    109:   if (ksp->pc_side == PC_RIGHT) {
    110:     KSP_PCApply(ksp,vsoln,vt1);
    111:     PCDiagonalScaleRight(ksp->pc,vt1,vsoln);
    112:   } else if (ksp->pc_side == PC_SYMMETRIC) {
    113:     PCApplySymmetricRight(ksp->pc,vsoln,vt1);
    114:     VecCopy(vt1,vsoln);
    115:   } else {
    116:     PCDiagonalScaleRight(ksp->pc,vsoln,vsoln);
    117:   }
    118:   return(0);
    119: }