Actual source code: itres.c
petsc-3.7.1 2016-05-15
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      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:   Mat            Amat,Pmat;

     49:   if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
     50:   PCGetOperators(ksp->pc,&Amat,&Pmat);
     51:   if (!ksp->guess_zero) {
     52:     /* skip right scaling since current guess already has it */
     53:     KSP_MatMult(ksp,Amat,vsoln,vt1);
     54:     VecCopy(vb,vt2);
     55:     VecAXPY(vt2,-1.0,vt1);
     56:     if (ksp->pc_side == PC_RIGHT) {
     57:       PCDiagonalScaleLeft(ksp->pc,vt2,vres);
     58:     } else if (ksp->pc_side == PC_LEFT) {
     59:         KSP_PCApply(ksp,vt2,vres);
     60:         PCDiagonalScaleLeft(ksp->pc,vres,vres);
     61:     } else if (ksp->pc_side == PC_SYMMETRIC) {
     62:       PCApplySymmetricLeft(ksp->pc,vt2,vres);
     63:     } else SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP, "Invalid preconditioning side %d", (int)ksp->pc_side);
     64:   } else {
     65:     VecCopy(vb,vt2);
     66:     if (ksp->pc_side == PC_RIGHT) {
     67:       PCDiagonalScaleLeft(ksp->pc,vb,vres);
     68:     } else if (ksp->pc_side == PC_LEFT) {
     69:       KSP_PCApply(ksp,vb,vres);
     70:       PCDiagonalScaleLeft(ksp->pc,vres,vres);
     71:     } else if (ksp->pc_side == PC_SYMMETRIC) {
     72:       PCApplySymmetricLeft(ksp->pc, vb, vres);
     73:     } else SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP, "Invalid preconditioning side %d", (int)ksp->pc_side);
     74:   }
     75:   return(0);
     76: }

     80: /*@
     81:    KSPUnwindPreconditioner - Unwinds the preconditioning in the solution. That is,
     82:      takes solution to the preconditioned problem and gets the solution to the
     83:      original problem from it.

     85:    Collective on KSP

     87:    Input Parameters:
     88: +  ksp  - iterative context
     89: .  vsoln - solution vector
     90: -  vt1   - temporary work vector

     92:    Output Parameter:
     93: .  vsoln - contains solution on output

     95:    Notes:
     96:    If preconditioning either symmetrically or on the right, this routine solves
     97:    for the correction to the unpreconditioned problem.  If preconditioning on
     98:    the left, nothing is done.

    100:    Level: advanced

    102: .keywords: KSP, unwind, preconditioner

    104: .seealso: KSPSetPCSide()
    105: @*/
    106: PetscErrorCode  KSPUnwindPreconditioner(KSP ksp,Vec vsoln,Vec vt1)
    107: {

    113:   if (!ksp->pc) {KSPGetPC(ksp,&ksp->pc);}
    114:   if (ksp->pc_side == PC_RIGHT) {
    115:     KSP_PCApply(ksp,vsoln,vt1);
    116:     PCDiagonalScaleRight(ksp->pc,vt1,vsoln);
    117:   } else if (ksp->pc_side == PC_SYMMETRIC) {
    118:     PCApplySymmetricRight(ksp->pc,vsoln,vt1);
    119:     VecCopy(vt1,vsoln);
    120:   } else {
    121:     PCDiagonalScaleRight(ksp->pc,vsoln,vsoln);
    122:   }
    123:   return(0);
    124: }