static PetscErrorCode KSPSolve_SpecEst(KSP ksp)
{
PetscErrorCode ierr;
KSP_SpecEst *spec = (KSP_SpecEst*)ksp->data;
PetscFunctionBegin;
if (spec->current) {
ierr = KSPSolve(spec->kspcheap,ksp->vec_rhs,ksp->vec_sol);CHKERRQ(ierr);
ierr = KSPSpecEstPropagateUp(ksp,spec->kspcheap);CHKERRQ(ierr);
} else {
PetscInt i,its,neig;
PetscReal *real,*imag,rad = 0;
ierr = KSPSolve(spec->kspest,ksp->vec_rhs,ksp->vec_sol);CHKERRQ(ierr);
ierr = KSPSpecEstPropagateUp(ksp,spec->kspest);CHKERRQ(ierr);
ierr = KSPComputeExtremeSingularValues(spec->kspest,&spec->max,&spec->min);CHKERRQ(ierr);
ierr = KSPGetIterationNumber(spec->kspest,&its);CHKERRQ(ierr);
ierr = PetscMalloc2(its,PetscReal,&real,its,PetscReal,&imag);CHKERRQ(ierr);
ierr = KSPComputeEigenvalues(spec->kspest,its,real,imag,&neig);CHKERRQ(ierr);
for (i=0; i<neig; i++) {
/* We would really like to compute w (nominally 1/radius) to minimize |1-wB|. Empirically it
is better to compute rad = |1-B| than rad = |B|. There must be a cheap way to do better. */
rad = PetscMax(rad,PetscRealPart(PetscSqrtScalar((PetscScalar)(PetscSqr(real[i]-1.) + PetscSqr(imag[i])))));
}
ierr = PetscFree2(real,imag);CHKERRQ(ierr);
spec->radius = rad;
ierr = KSPChebyshevSetEigenvalues(spec->kspcheap,spec->max*spec->maxfactor,spec->min*spec->minfactor);CHKERRQ(ierr);
ierr = KSPRichardsonSetScale(spec->kspcheap,spec->richfactor/spec->radius);
ierr = PetscInfo3(ksp,"Estimated singular value min=%G max=%G, spectral radius=%G",spec->min,spec->max,spec->radius);CHKERRQ(ierr);
spec->current = PETSC_TRUE;
}
PetscFunctionReturn(0);
}
static PetscErrorCode KSPSetFromOptions_Chebyshev(PetscOptions *PetscOptionsObject,KSP ksp)
{
KSP_Chebyshev *cheb = (KSP_Chebyshev*)ksp->data;
PetscErrorCode ierr;
PetscInt neigarg = 2, nestarg = 4;
PetscReal eminmax[2] = {0., 0.};
PetscReal tform[4] = {PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE};
PetscBool flgeig, flgest;
PetscFunctionBegin;
ierr = PetscOptionsHead(PetscOptionsObject,"KSP Chebyshev Options");CHKERRQ(ierr);
ierr = PetscOptionsInt("-ksp_chebyshev_esteig_steps","Number of est steps in Chebyshev","",cheb->eststeps,&cheb->eststeps,NULL);CHKERRQ(ierr);
ierr = PetscOptionsRealArray("-ksp_chebyshev_eigenvalues","extreme eigenvalues","KSPChebyshevSetEigenvalues",eminmax,&neigarg,&flgeig);CHKERRQ(ierr);
if (flgeig) {
if (neigarg != 2) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_INCOMP,"-ksp_chebyshev_eigenvalues: must specify 2 parameters, min and max eigenvalues");
ierr = KSPChebyshevSetEigenvalues(ksp, eminmax[1], eminmax[0]);CHKERRQ(ierr);
}
ierr = PetscOptionsRealArray("-ksp_chebyshev_esteig","estimate eigenvalues using a Krylov method, then use this transform for Chebyshev eigenvalue bounds","KSPChebyshevEstEigSet",tform,&nestarg,&flgest);CHKERRQ(ierr);
if (flgest) {
switch (nestarg) {
case 0:
ierr = KSPChebyshevEstEigSet(ksp,PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE);CHKERRQ(ierr);
break;
case 2: /* Base everything on the max eigenvalues */
ierr = KSPChebyshevEstEigSet(ksp,PETSC_DECIDE,tform[0],PETSC_DECIDE,tform[1]);CHKERRQ(ierr);
break;
case 4: /* Use the full 2x2 linear transformation */
ierr = KSPChebyshevEstEigSet(ksp,tform[0],tform[1],tform[2],tform[3]);CHKERRQ(ierr);
break;
default: SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_INCOMP,"Must specify either 0, 2, or 4 parameters for eigenvalue estimation");
}
}
/* We need to estimate eigenvalues; need to set this here so that KSPSetFromOptions() is called on the estimator */
if ((cheb->emin == 0. || cheb->emax == 0.) && !cheb->kspest) {
ierr = KSPChebyshevEstEigSet(ksp,PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE);CHKERRQ(ierr);
}
if (cheb->kspest) {
ierr = PetscOptionsBool("-ksp_chebyshev_esteig_random","Use random right hand side for estimate","KSPChebyshevEstEigSetUseRandom",cheb->userandom,&cheb->userandom,NULL);CHKERRQ(ierr);
if (cheb->userandom) {
const char *ksppre;
if (!cheb->random) {
ierr = PetscRandomCreate(PetscObjectComm((PetscObject)ksp),&cheb->random);CHKERRQ(ierr);
}
ierr = KSPGetOptionsPrefix(cheb->kspest, &ksppre);CHKERRQ(ierr);
ierr = PetscObjectSetOptionsPrefix((PetscObject)cheb->random,ksppre);CHKERRQ(ierr);
ierr = PetscRandomSetFromOptions(cheb->random);CHKERRQ(ierr);
}
ierr = KSPSetFromOptions(cheb->kspest);CHKERRQ(ierr);
}
ierr = PetscOptionsTail();CHKERRQ(ierr);
PetscFunctionReturn(0);
}
void PETSC_STDCALL kspchebyshevseteigenvalues_(KSP ksp,PetscReal *emax,PetscReal *emin, int *__ierr ){
*__ierr = KSPChebyshevSetEigenvalues(
(KSP)PetscToPointer((ksp) ),*emax,*emin);
}
