[petsc-users] Incorrect eigenvalues

[Jose E. Roman]

[Please do not send queries to both petsc-users and slepc-maint, only one of them is enough.]

It seems that you are mixing a random number of options that make little sense. You cannot use preonly+jacobi to solve linear systems, even less in the case of the eps_interval option. For computing eigenvalues in an interval, follow the instructions in section 3.4.5 of the users manual. In particular, preonly+cholesky is required. Also, if done with MUMPS the option -mat_mumps_icntl_13 1 is also needed. Furthermore, I don't see that you are using -st_type sinvert, so I guess some options are inserted in the source code, which you did not show.

Jose


> El 18 jul 2016, a las 21:01, Hassan Md Mahmudulla <mhassan at miners.utep.edu> escribió:
> 
> Hi all,
> I have been trying to solve generalized eigenvalue problem using matrices of size 10K. Sparsity of the matrix is 6%. I am using the following command 
> 
> ./solver -f1 hamold.petsc -f2 ovlbaby.petsc -st_ksp_type preonly -st_pc_type jacobi -st_pc_factor_mat_solver_package mumps -eps_interval -2,0 -eps_nev 1000
> 
> 	• solver is the program
> 	• f1 and f2 are the input file for both matrices in petsc binary (mpiaij)
> I am getting the following output:
> 
>  
> Generalized eigenproblem stored in file.
> 
>  Reading REAL matrices from binary files...
>  TYPE OF MATRIX A: mpiaij
>  TYPE OF MATRIX B: mpiaij
>  Solving for Eigen values...
>   Solved! 
>   1: -9771.8339             0
>   2: -9559.8347             0
>   3: -9408.5603             0
>   4:  -9387.423             0
>   5: -9235.9137             0
>   6: -9102.5334             0
>   7: -9098.1307             0
>   8: -8970.3594             0
>   9: -8854.4964             0
>   10: -8850.3629             0
>   11: -8736.6619             0
>   12: -8637.1749             0
>   13:  -8628.214             0
>   14: -8524.2494             0
>   15: -8440.0801             0
>   16: -8424.1789             0
>   17: -8327.5389             0
>   18: -8257.7763             0
>   19: -8233.9564             0
>   20: -8143.1251             0
>   21: -8086.9865             0
>   22: -8054.7899             0
>   23: -7968.7355             0
>   24: -7925.5421             0
>   25: -7884.7777             0
>   26: -7802.7577             0
>   27:  -7771.913             0
>   28:  -7722.537             0
>   29: -7643.9943             0
>   30: -7624.9684             0
>  
>   .........................
>   .........................
>  
>  541: -24.947288             0
>   542: -24.945875             0
>   543:  -24.94017             0
>  
> 
> First column is the eigenvalues. 
> My concern is, 
> 	• Eigenvalues are not right
> 	• I defined the interval but still it's giving me eigenvalues outside of that interval
>  Please help me out.
> 
> M Hassan