1: /*$Id: itres.c,v 1.54 2001/08/07 03:03:45 balay Exp $*/

 3:  #include src/sles/ksp/kspimpl.h

  5: #undef __FUNCT__  
  7: /*@C
  8:    KSPInitialResidual - Computes the residual.

 10:    Collective on KSP

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

 18:    Notes:
 19:    This routine assumes that an iterative method, designed for
 20: $     A x = b
 21:    will be used with a preconditioner, C, such that the actual problem is either
 22: $     AC u = f (right preconditioning) or
 23: $     CA x = Cf (left preconditioning).

 25:    Level: developer

 27: .keywords: KSP, residual

 29: .seealso:  KSPMonitor()
 30: @*/
 31: int KSPInitialResidual(KSP ksp,Vec vsoln,Vec vt1,Vec vt2,Vec vres,Vec vb)
 32: {
 33:   PetscScalar   mone = -1.0;
 34:   MatStructure  pflag;
 35:   Mat           Amat,Pmat;
 36:   int           ierr;

 40:   PCGetOperators(ksp->B,&Amat,&Pmat,&pflag);
 41:   if (!ksp->guess_zero) {
 42:     /* skip right scaling since current guess already has it */
 43:     KSP_MatMult(ksp,Amat,vsoln,vt1);
 44:     VecCopy(vb,vt2);
 45:     VecAXPY(&mone,vt1,vt2);
 46:     (ksp->pc_side == PC_RIGHT)?(VecCopy(vt2,vres)):(KSP_PCApply(ksp,ksp->B,vt2,vres));
 47:     PCDiagonalScaleLeft(ksp->B,vres,vres);
 48:   } else {
 49:     if (ksp->pc_side == PC_RIGHT) {
 50:       PCDiagonalScaleLeft(ksp->B,vb,vres);
 51:     } else if (ksp->pc_side == PC_LEFT) {
 52:       KSP_PCApply(ksp,ksp->B,vb,vres);
 53:       PCDiagonalScaleLeft(ksp->B,vres,vres);
 54:     } else if (ksp->pc_side == PC_SYMMETRIC) {
 55:       PCApplySymmetricLeft(ksp->B, vb, vres);
 56:     } else {
 57:       SETERRQ1(PETSC_ERR_SUP, "Invalid preconditioning side %d", ksp->pc_side);
 58:   }

 60:   }
 61:   return(0);
 62: }

 64: #undef __FUNCT__  
 66: /*@
 67:    KSPUnwindPreconditioner - Unwinds the preconditioning in the solution. That is,
 68:      takes solution to the preconditioned problem and gets the solution to the 
 69:      original problem from it.

 71:    Collective on KSP

 73:    Input Parameters:
 74: +  ksp  - iterative context
 75: .  vsoln - solution vector 
 76: -  vt1   - temporary work vector

 78:    Output Parameter:
 79: .  vsoln - contains solution on output  

 81:    Notes:
 82:    If preconditioning either symmetrically or on the right, this routine solves 
 83:    for the correction to the unpreconditioned problem.  If preconditioning on 
 84:    the left, nothing is done.

 86:    Level: advanced

 88: .keywords: KSP, unwind, preconditioner

 90: .seealso: KSPSetPreconditionerSide()
 91: @*/
 92: int KSPUnwindPreconditioner(KSP ksp,Vec vsoln,Vec vt1)
 93: {

 98:   if (ksp->pc_side == PC_RIGHT) {
 99:     KSP_PCApply(ksp,ksp->B,vsoln,vt1);
100:     PCDiagonalScaleRight(ksp->B,vt1,vsoln);
101:   } else if (ksp->pc_side == PC_SYMMETRIC) {
102:     PCApplySymmetricRight(ksp->B,vsoln,vt1);
103:     VecCopy(vt1,vsoln);
104:   } else {
105:     PCDiagonalScaleRight(ksp->B,vsoln,vsoln);
106:   }
107:   return(0);
108: }