[petsc-users] SLEPc generalized eigenvalue problem question?

[Jose E. Roman]

El 02/08/2011, a las 09:24, John Chludzinski escribió:

> Jose,
> 
> I used:
> 
> MatCreateSeqAIJ(PETSC_COMM_SELF, n, n, 0, cnt, &A);
> MatSetValue(A, i, j, *(a+i*SIZE+j), INSERT_VALUES);
> 
> to create the input matrices.  Their sizes collapsed dramatically: from 192208072 to 239944. But again, using: ./ex7.exe -f1 k.dat -f2 m.dat -eps_gen_hermitian -eps_smallest_real > x.out 2>&1, I get:
> 
> Generalized eigenproblem stored in file.
> 
> Reading REAL matrices from binary files...
> Number of iterations of the method: 500
> Number of linear iterations of the method: 4009
> Solution method: krylovschur
> 
> Number of requested eigenvalues: 1
> Stopping condition: tol=1e-07, maxit=500
> Number of converged approximate eigenpairs: 0
> 
> I'm really only interested in the least 50 eigenvalues.
> 
> Smallest 10 eigenvalues
> -0.000019
> -0.000004
> -0.000000
> 0.000005
> 0.000012
> 0.000016
> 2.795284
> 2.795307
> 21.235339
> 21.235340
> 81.582017
> 
> Largest 10 eigenvalues
> 176431487319.625000
> 176431532012.467468
> 176431562378.361359
> 176435480628.136292
> 176435488209.944031
> 176435555689.747253
> 176435563270.922424
> 663312473823.916260
> 663312473823.917969
> 663312666285.928589
> 663312666285.929810
> 

You will never get convergence to the small eigenvalues in this way, since the largest ones are huge. Try something like:
./ex7.exe -f1 k.dat -f2 m.dat -eps_gen_hermitian -st_type sinvert -eps_target 1.0

Jose