[petsc-users] Slepc: Computing first 4 smallest eigenvalues and eigenvectors of a large graph Laplacian

[Bodhisatta Pramanik]

*The error is in EPSComputeError(), not in EPSSolve(). Did you modify the
state of the EPS object between EPSSolve() and EPSComputeError()?*

I am not modifying the eps object. I have copied a part of the code where I
am computing the eigenvectors.

        EPSCreate(PETSC_COMM_WORLD,&eps);
        EPSSetOperators(eps,m.Lpl,NULL);
        EPSSetProblemType(eps,EPS_HEP);
        EPSSetFromOptions(eps);

        EPSSolve(eps);  //Solving for the eigenvalues

        EPSGetIterationNumber(eps,&its);
        PetscPrintf(PETSC_COMM_WORLD,"Number of iterations of the method:
%D\n",its);
        EPSGetType(eps,&type);
        PetscPrintf(PETSC_COMM_WORLD,"Solution Method: %s\n\n",type);
        EPSGetTolerances(eps,&get_tol,&maxit);
        PetscPrintf(PETSC_COMM_WORLD,"Stopping condition: tol=%.4g,
maxit=%D\n",(double)get_tol,maxit);
        EPSGetConverged(eps,&nconv);
        PetscPrintf(PETSC_COMM_WORLD, "Number of converged eigenpairs:
%D\n\n",nconv);
        if(nconv>0)
        {
                PetscPrintf(PETSC_COMM_WORLD,
                        "       k       ||Ax-kx||/||kx||\n"
                        "-------------- ----------------\n");
                for(i=0;i<nconv;i++)
                {
                        EPSGetEigenpair(eps,i,&kr,&ki,xr,xi);
                        EPSComputeError(eps,i,EPS_ERROR_RELATIVE,&error);
                        re = PetscRealPart(kr);
                        im = PetscImaginaryPart(kr);

                        re = kr;
                        im = ki;
                        if(im!=0.0) {
                                PetscPrintf(PETSC_COMM_WORLD," %9f%+9fi
%12g\n",(double)re,(double)im,(double)error);
                        }
                        else {
                                PetscPrintf(PETSC_COMM_WORLD,"     %12f
 %12g\n",(double)re,(double)error);
                        }
                }
                PetscPrintf(PETSC_COMM_WORLD,"\n");
        }

        EPSDestroy(&eps);
        VecDestroy(&xr);
        VecDestroy(&xi);
}

This is what I pass through my command line:
./RunPart -eps_type jd -eps_nev 3 -st_ksp_type cg -st_ksp_rtol 0.001
-eps_tol 0.001 -st_pc_type bjacobi -eps_smallest_real


*In graph partitioning, I would strongly recommend deflating the
eigenvector corresponding to the zero eigenvalue, as is done in ex11.c:*
        I have tried doing this but for some reason the eigenvalues fail to
converge.



On Sun, Mar 26, 2017 at 2:41 AM, Jose E. Roman <jroman at dsic.upv.es> wrote:

>
> > El 26 mar 2017, a las 6:08, Bodhisatta Pramanik <bodhi91 at iastate.edu>
> escribió:
> >
> > Send all the output in the error message:
> >
> > [0]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
> > [0]PETSC ERROR: Object is in wrong state
> > [0]PETSC ERROR: Must call EPSSolve() first: Parameter #1
> > [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html
> for trouble shooting.
> > [0]PETSC ERROR: Petsc Release Version 3.7.5, Jan, 01, 2017
> > [0]PETSC ERROR: ./RunPart on a arch-linux2-c-debug named
> research-5.ece.iastate.edu by bodhi91 Sat Mar 25 22:33:56 2017
> > [0]PETSC ERROR: Configure options --with-cc=gcc --with-css=g++
> -with-fc=gfortran --download-fblaslapack --download-mpich
> > [0]PETSC ERROR: #10468 EPSComputeError() line 643 in
> /tmp/Bodhi/slepc-3.7.3/src/eps/interface/epssolve.c
> >          0.000000     2.0795e-317
> >
>
> The error is in EPSComputeError(), not in EPSSolve(). Did you modify the
> state of the EPS object between EPSSolve() and EPSComputeError()?
>
> In graph partitioning, I would strongly recommend deflating the
> eigenvector corresponding to the zero eigenvalue, as is done in ex11.c:
> http://slepc.upv.es/documentation/current/src/eps/
> examples/tutorials/ex11.c.html
>
> Jose
>
>


-- 
*Bodhisatta Pramanik,*
*Graduate Student,*
*Department of Electrical and Computer Engineering,*
*301 Durham,*
*Iowa State University,*
*Ames,Iowa 50011,*
bodhi91 at iastate.edu
*515-735-6300*
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