PetscErrorCode PCMGACycle_Private(PC pc,PC_MG_Levels **mglevels)
{
PetscErrorCode ierr;
PetscInt i,l = mglevels[0]->levels;
PetscFunctionBegin;
/* compute RHS on each level */
for (i=l-1; i>0; i--) {
if (mglevels[i]->eventinterprestrict) {ierr = PetscLogEventBegin(mglevels[i]->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
ierr = MatRestrict(mglevels[i]->restrct,mglevels[i]->b,mglevels[i-1]->b);CHKERRQ(ierr);
if (mglevels[i]->eventinterprestrict) {ierr = PetscLogEventEnd(mglevels[i]->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
}
/* solve separately on each level */
for (i=0; i<l; i++) {
ierr = VecSet(mglevels[i]->x,0.0);CHKERRQ(ierr);
if (mglevels[i]->eventsmoothsolve) {ierr = PetscLogEventBegin(mglevels[i]->eventsmoothsolve,0,0,0,0);CHKERRQ(ierr);}
ierr = KSPSolve(mglevels[i]->smoothd,mglevels[i]->b,mglevels[i]->x);CHKERRQ(ierr);
ierr = KSPCheckSolve(mglevels[i]->smoothd,pc,mglevels[i]->x);CHKERRQ(ierr);
if (mglevels[i]->eventsmoothsolve) {ierr = PetscLogEventEnd(mglevels[i]->eventsmoothsolve,0,0,0,0);CHKERRQ(ierr);}
}
for (i=1; i<l; i++) {
if (mglevels[i]->eventinterprestrict) {ierr = PetscLogEventBegin(mglevels[i]->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
ierr = MatInterpolateAdd(mglevels[i]->interpolate,mglevels[i-1]->x,mglevels[i]->x,mglevels[i]->x);CHKERRQ(ierr);
if (mglevels[i]->eventinterprestrict) {ierr = PetscLogEventEnd(mglevels[i]->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
}
PetscFunctionReturn(0);
}
/*
Performs the FAS coarse correction as:
fine problem: F(x) = b
coarse problem: F^c(x^c) = b^c
b^c = F^c(Rx) - R(F(x) - b)
*/
PetscErrorCode SNESFASCoarseCorrection(SNES snes, Vec X, Vec F, Vec X_new)
{
PetscErrorCode ierr;
Vec X_c, Xo_c, F_c, B_c;
SNESConvergedReason reason;
SNES next;
Mat restrct, interpolate;
SNES_FAS *fasc;
PetscFunctionBegin;
ierr = SNESFASCycleGetCorrection(snes, &next);CHKERRQ(ierr);
if (next) {
fasc = (SNES_FAS*)next->data;
ierr = SNESFASCycleGetRestriction(snes, &restrct);CHKERRQ(ierr);
ierr = SNESFASCycleGetInterpolation(snes, &interpolate);CHKERRQ(ierr);
X_c = next->vec_sol;
Xo_c = next->work[0];
F_c = next->vec_func;
B_c = next->vec_rhs;
if (fasc->eventinterprestrict) {ierr = PetscLogEventBegin(fasc->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
ierr = SNESFASRestrict(snes,X,Xo_c);CHKERRQ(ierr);
/* restrict the defect: R(F(x) - b) */
ierr = MatRestrict(restrct, F, B_c);CHKERRQ(ierr);
if (fasc->eventinterprestrict) {ierr = PetscLogEventEnd(fasc->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
if (fasc->eventresidual) {ierr = PetscLogEventBegin(fasc->eventresidual,0,0,0,0);CHKERRQ(ierr);}
/* F_c = F^c(Rx) - R(F(x) - b) since the second term was sitting in next->vec_rhs */
ierr = SNESComputeFunction(next, Xo_c, F_c);CHKERRQ(ierr);
if (fasc->eventresidual) {ierr = PetscLogEventEnd(fasc->eventresidual,0,0,0,0);CHKERRQ(ierr);}
/* solve the coarse problem corresponding to F^c(x^c) = b^c = F^c(Rx) - R(F(x) - b) */
ierr = VecCopy(B_c, X_c);CHKERRQ(ierr);
ierr = VecCopy(F_c, B_c);CHKERRQ(ierr);
ierr = VecCopy(X_c, F_c);CHKERRQ(ierr);
/* set initial guess of the coarse problem to the projected fine solution */
ierr = VecCopy(Xo_c, X_c);CHKERRQ(ierr);
/* recurse to the next level */
ierr = SNESSetInitialFunction(next, F_c);CHKERRQ(ierr);
ierr = SNESSolve(next, B_c, X_c);CHKERRQ(ierr);
ierr = SNESGetConvergedReason(next,&reason);CHKERRQ(ierr);
if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
snes->reason = SNES_DIVERGED_INNER;
PetscFunctionReturn(0);
}
/* correct as x <- x + I(x^c - Rx)*/
ierr = VecAXPY(X_c, -1.0, Xo_c);CHKERRQ(ierr);
if (fasc->eventinterprestrict) {ierr = PetscLogEventBegin(fasc->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
ierr = MatInterpolateAdd(interpolate, X_c, X, X_new);CHKERRQ(ierr);
if (fasc->eventinterprestrict) {ierr = PetscLogEventEnd(fasc->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
}
PetscFunctionReturn(0);
}
PetscErrorCode PCMGMCycle_Private(PC pc,PC_MG_Levels **mglevelsin,PCRichardsonConvergedReason *reason)
{
PC_MG *mg = (PC_MG*)pc->data;
PC_MG_Levels *mgc,*mglevels = *mglevelsin;
PetscErrorCode ierr;
PetscInt cycles = (mglevels->level == 1) ? 1 : (PetscInt) mglevels->cycles;
PC subpc;
PCFailedReason pcreason;
PetscFunctionBegin;
if (mglevels->eventsmoothsolve) {ierr = PetscLogEventBegin(mglevels->eventsmoothsolve,0,0,0,0);CHKERRQ(ierr);}
ierr = KSPSolve(mglevels->smoothd,mglevels->b,mglevels->x);CHKERRQ(ierr); /* pre-smooth */
ierr = KSPGetPC(mglevels->smoothd,&subpc);CHKERRQ(ierr);
ierr = PCGetSetUpFailedReason(subpc,&pcreason);CHKERRQ(ierr);
if (pcreason) {
pc->failedreason = PC_SUBPC_ERROR;
}
if (mglevels->eventsmoothsolve) {ierr = PetscLogEventEnd(mglevels->eventsmoothsolve,0,0,0,0);CHKERRQ(ierr);}
if (mglevels->level) { /* not the coarsest grid */
if (mglevels->eventresidual) {ierr = PetscLogEventBegin(mglevels->eventresidual,0,0,0,0);CHKERRQ(ierr);}
ierr = (*mglevels->residual)(mglevels->A,mglevels->b,mglevels->x,mglevels->r);CHKERRQ(ierr);
if (mglevels->eventresidual) {ierr = PetscLogEventEnd(mglevels->eventresidual,0,0,0,0);CHKERRQ(ierr);}
/* if on finest level and have convergence criteria set */
if (mglevels->level == mglevels->levels-1 && mg->ttol && reason) {
PetscReal rnorm;
ierr = VecNorm(mglevels->r,NORM_2,&rnorm);CHKERRQ(ierr);
if (rnorm <= mg->ttol) {
if (rnorm < mg->abstol) {
*reason = PCRICHARDSON_CONVERGED_ATOL;
ierr = PetscInfo2(pc,"Linear solver has converged. Residual norm %g is less than absolute tolerance %g\n",(double)rnorm,(double)mg->abstol);CHKERRQ(ierr);
} else {
*reason = PCRICHARDSON_CONVERGED_RTOL;
ierr = PetscInfo2(pc,"Linear solver has converged. Residual norm %g is less than relative tolerance times initial residual norm %g\n",(double)rnorm,(double)mg->ttol);CHKERRQ(ierr);
}
PetscFunctionReturn(0);
}
}
mgc = *(mglevelsin - 1);
if (mglevels->eventinterprestrict) {ierr = PetscLogEventBegin(mglevels->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
ierr = MatRestrict(mglevels->restrct,mglevels->r,mgc->b);CHKERRQ(ierr);
if (mglevels->eventinterprestrict) {ierr = PetscLogEventEnd(mglevels->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
ierr = VecSet(mgc->x,0.0);CHKERRQ(ierr);
while (cycles--) {
ierr = PCMGMCycle_Private(pc,mglevelsin-1,reason);CHKERRQ(ierr);
}
if (mglevels->eventinterprestrict) {ierr = PetscLogEventBegin(mglevels->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
ierr = MatInterpolateAdd(mglevels->interpolate,mgc->x,mglevels->x,mglevels->x);CHKERRQ(ierr);
if (mglevels->eventinterprestrict) {ierr = PetscLogEventEnd(mglevels->eventinterprestrict,0,0,0,0);CHKERRQ(ierr);}
if (mglevels->eventsmoothsolve) {ierr = PetscLogEventBegin(mglevels->eventsmoothsolve,0,0,0,0);CHKERRQ(ierr);}
ierr = KSPSolve(mglevels->smoothu,mglevels->b,mglevels->x);CHKERRQ(ierr); /* post smooth */
if (mglevels->eventsmoothsolve) {ierr = PetscLogEventEnd(mglevels->eventsmoothsolve,0,0,0,0);CHKERRQ(ierr);}
}
PetscFunctionReturn(0);
}