[petsc-users] EPSKrylovSchurSetDetectZeros() not working

[Hassan Md Mahmudulla]

Hi Jose,

Here is the part of the code:


  ierr = STSetType(st,STSINVERT);CHKERRQ(ierr);

  ierr = STGetKSP(st,&ksp);CHKERRQ(ierr);
  ierr = KSPSetType(ksp,KSPPREONLY);CHKERRQ(ierr);
  ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
  ierr = PCSetType(pc,PCCHOLESKY);CHKERRQ(ierr);

#if defined(PETSC_HAVE_MUMPS)
#if defined(PETSC_USE_COMPLEX)
  SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"Spectrum slicing with MUMPS is not available for complex scalars");
#endif
  ierr = PetscPrintf(PETSC_COMM_WORLD, "PETSC_HAVE_MUMPS\n");CHKERRQ(ierr);
  ierr = EPSKrylovSchurSetDetectZeros(eps,PETSC_TRUE);CHKERRQ(ierr);  /* enforce zero detection */
  ierr = PCFactorSetMatSolverPackage(pc,MATSOLVERMUMPS);CHKERRQ(ierr);
  /*
     Add several MUMPS options (currently there is no better way of setting this in program):
     '-mat_mumps_icntl_13 1': turn off ScaLAPACK for matrix inertia
     '-mat_mumps_icntl_24 1': detect null pivots in factorization (for the case that a shift is equal to an eigenvalue)
     '-mat_mumps_cntl_3 <tol>': a tolerance used for null pivot detection (must be larger than machine epsilon)

     Note: depending on the interval, it may be necessary also to increase the workspace:
     '-mat_mumps_icntl_14 <percentage>': increase workspace with a percentage (50, 100 or more)
  */
  ierr = PetscOptionsInsertString(NULL,"-mat_mumps_icntl_13 1 -mat_mumps_icntl_24 1 -mat_mumps_cntl_3 1e-12");CHKERRQ(ierr);
#endif

  /*
     Set solver parameters at runtime
  */
  ierr = EPSSetFromOptions(eps);CHKERRQ(ierr);


I am using MUMPS. Actually it's the example I said before. I didn't modify it that much.



M Hassan

________________________________
From: Jose E. Roman <jroman at dsic.upv.es>
Sent: Sunday, July 24, 2016 1:27:04 PM
To: Hassan Md Mahmudulla
Cc: petsc-users at mcs.anl.gov
Subject: Re: [petsc-users] EPSKrylovSchurSetDetectZeros() not working


> El 24 jul 2016, a las 19:50, Hassan Md Mahmudulla <mhassan at miners.utep.edu> escribió:
>
> Hi,
> I am solving a generalized eigenvalue problem using spectrum slicing. I am using this example (http://slepc.upv.es/documentation/current/src/eps/examples/tutorials/ex25.c.html) as it is. Part of the code is:
> ierr =EPSKrylovSchurSetDetectZeros(eps,PETSC_TRUE);CHKERRQ(ierr);
>
> But I am getting the following:
>
> [0]PETSC ERROR: Mismatch between number of values found and information from inertia, consider using EPSKrylovSchurSetDetectZeros()
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
>
> It seems the input PETSC_TRUE is not working for EPSKrylovSchurSetDetectZeros(). Any idea?
>
> M Hassan

It seems that you are not using MUMPS. Spectrum slicing can be used with PETSc's Cholesky, but for guaranteed robustness it is necessary to use MUMPS.

Jose

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