[petsc-users] Petsc has generated inconsistent data - Divide by zero!

[Jed Brown]

On Fri, Jul 8, 2011 at 08:26, TAY wee-beng <zonexo at gmail.com> wrote:

> [0]PETSC ERROR: KSPSolve_BCGS() line 75 in
> src/ksp/ksp/impls/bcgs/C:\Codes\PETSC
> -~1.1-P\src\ksp\ksp\impls\bcgs\bcgs.c
>

    ierr = KSP_PCApplyBAorAB(ksp,P,V,T);CHKERRQ(ierr);  /*   v <- K p
    */
    ierr = VecDot(V,RP,&d1);CHKERRQ(ierr);
    if (d1 == 0.0) SETERRQ(PETSC_ERR_PLIB,"Divide by zero");

I suspect your preconditioner is singular. What options are you running
with? What happens if you use -ksp_type gmres -ksp_gmres_restart 1000
-ksp_gmres_modifiedgramschmidt -ksp_monitor_true_residual? Also do the same
run with -ksp_type fgmres.
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