<div><font face="courier new,monospace">Jose,</font></div><div><font face="courier new,monospace"><br></font></div><div><font face="courier new,monospace">I used:</font></div><div><font face="courier new,monospace"><br></font></div>
<div><div style="margin-left: 40px !important"><font face="courier new,monospace">MatCreateSeqAIJ(PETSC_COMM_SELF, n, n, 0, cnt, &A);</font><div><font face="courier new,monospace">MatSetValue(A, i, j, *(a+i*SIZE+j), INSERT_VALUES);</font></div>
<div><font face="courier new,monospace"><br></font></div></div></div><div style="margin-left: 0px !important"><div><font face="courier new,monospace">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:</font></div>
<div><font face="courier new,monospace"><br></font></div><div><div style="margin-left: 40px !important"><font face="courier new,monospace">Generalized eigenproblem stored in file.</font><div><font face="courier new,monospace"><br>
</font></div><div><font face="courier new,monospace"> Reading REAL matrices from binary files...</font></div><div><font face="courier new,monospace"> Number of iterations of the method: 500</font></div><div><font face="courier new,monospace"> Number of linear iterations of the method: 4009</font></div>
<div><font face="courier new,monospace"> Solution method: krylovschur</font></div><div><font face="courier new,monospace"><br></font></div><div><font face="courier new,monospace"> Number of requested eigenvalues: 1</font></div>
<div><font face="courier new,monospace"> Stopping condition: tol=1e-07, maxit=500</font></div><div><font face="courier new,monospace"> Number of converged approximate eigenpairs: 0</font></div><div><font face="courier new,monospace"><br>
</font></div></div></div></div><div><font face="courier new,monospace">I'm really only interested in the least 50 eigenvalues.</font><font face="courier new,monospace"><br></font></div><div><font face="courier new,monospace"><br>
</font></div><div><font face="courier new,monospace">Smallest 10 eigenvalues</font></div><div><font face="courier new,monospace">-0.000019</font></div><div><font face="courier new,monospace">-0.000004</font></div><div><font face="courier new,monospace">-0.000000</font></div>
<div><font face="courier new,monospace"> 0.000005</font></div><div><font face="courier new,monospace"> 0.000012</font></div><div><font face="courier new,monospace"> 0.000016</font></div><div><font face="courier new,monospace"> 2.795284</font></div>
<div><font face="courier new,monospace"> 2.795307</font></div><div><font face="courier new,monospace"> 21.235339</font></div><div><font face="courier new,monospace"> 21.235340</font></div><div><font face="courier new,monospace"> 81.582017</font></div>
<div><font face="courier new,monospace"><br></font></div><div><font face="courier new,monospace">Largest 10 eigenvalues</font></div><div><font face="courier new,monospace">176431487319.625000</font></div><div><font face="courier new,monospace">176431532012.467468</font></div>
<div><font face="courier new,monospace">176431562378.361359</font></div><div><font face="courier new,monospace">176435480628.136292</font></div><div><font face="courier new,monospace">176435488209.944031</font></div><div>
<font face="courier new,monospace">176435555689.747253</font></div><div><font face="courier new,monospace">176435563270.922424</font></div><div><font face="courier new,monospace">663312473823.916260</font></div><div><font face="courier new,monospace">663312473823.917969</font></div>
<div><font face="courier new,monospace">663312666285.928589</font></div><div><font face="courier new,monospace">663312666285.929810</font></div><div><font face="courier new,monospace"><br></font></div><div style="margin-left: 40px !important">
<div style="margin-left: 40px !important"><font face="courier new,monospace"><div class="gmail_quote">On Mon, Aug 1, 2011 at 1:46 PM, Jose E. Roman <span dir="ltr"><<a href="mailto:jroman@dsic.upv.es">jroman@dsic.upv.es</a>></span> wrote:<div>
<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div>
El 01/08/2011, a las 19:27, John Chludzinski escribió:</div><div>
<br></div><div><div class="h5"><div>
> I create 2 matrices using:</div><div>
></div><div>
> MatCreateSeqDense(PETSC_COMM_SELF, n, n, Ka, &A);</div><div>
> MatCreateSeqDense(PETSC_COMM_SELF, n, n, Kb, &B);</div><div>
></div><div>
> These matrices are 99% zeros ( 16,016,004 entries and 18660 non-zeros). They are symmetric and real. Their tri-diagonal elements are non-zero plus a few other entries.</div><div>
></div><div>
> I tried to use ex7 for the generalized eigenvalue problem:</div><div>
></div><div>
> ./ex7.exe -f1 k.dat -f2 m.dat -eps_gen_hermitian -eps_smallest_real > x.out 2>&1</div><div>
></div><div>
> without specifying an EPS and get:</div><div>
></div><div>
> Generalized eigenproblem stored in file.</div><div>
></div><div>
> Reading REAL matrices from binary files...</div><div>
> Number of iterations of the method: 500</div><div>
> Number of linear iterations of the method: 4009</div><div>
> Solution method: krylovschur</div><div>
></div><div>
> Number of requested eigenvalues: 1</div><div>
> Stopping condition: tol=1e-07, maxit=500</div><div>
> Number of converged approximate eigenpairs: 0</div><div>
></div><div>
> Is krylovschur inappropriate for this problem or have I set up the problem incorrectly by using MatCreateSeqDense(...) to create the matrix input files in PETSc binary form?</div><div>
></div><div>
> ---John</div><div>
<br></div><div>
<br></div><div>
<br></div></div></div>The solver has reached the maximum number of iterations. Do you want to compute the leftmost part of the spectrum? Are those eigenvalues (relatively) large in magnitude? I guess not. If you need the smallest eigenvalues, instead of computing the smallest eigenvalues of (K,M) try computing the largest eigenvalues of (M,K) and then compute the reciprocals. Also, have a look at the chapter on spectral transformations.<div>
<br></div><div>
And of course do not use dense matrices, as pointed out by Matt.</div><div>
<font color="#888888"></font></div><div>
Jose<div>
<div>
</div></div></div></blockquote></div></font></div></div><div><br></div>