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Dear All,</div>
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I am planning on using slepc to do a large number of eigenvalue calculations</div>
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of a generalized eigenvalue problem, called from a program written in fortran using MPI.<br>
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Thus far I have successfully installed the slepc/PETSc software, both locally and on a cluster,</div>
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and on smaller test problems everything is working well; the matrices are efficiently and
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correctly constructed and slepc returns the correct spectrum. I am just now starting to move</div>
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towards now solving the full-size 'production run' problems, and would appreciate some
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general advice on how to improve the solver's performance.</div>
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In particular, I am currently trying to solve the problem Ax = lambda Bx whose matrices
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are of size 50000 (this is the smallest 'production run' problem I will be tackling), and are
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complex, non-Hermitian. In most cases I aim to find the eigenvalues with the largest real part,
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although in other cases I will also be interested in finding the eigenvalues whose real part
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is close to zero.<br>
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A)<br>
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Calling slepc 's EPS solver with the following options:</div>
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<span style="color: rgb(12, 100, 192);">-</span><span style="color: rgb(12, 100, 192);">eps_nev 10 -log_view -eps_view -eps_max_it 600 -eps_ncv 140 -eps_tol 5.0e-6 -eps_largest_real -eps_monitor :monitor_output.txt</span><br>
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led to the code successfully running, but failing to find any eigenvalues within the maximum 600 iterations
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(examining the monitor output it did appear to be very slowly approaching convergence).<br>
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B)<br>
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On the same problem I have also tried a shift-invert transformation using the options</div>
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<span style="color: rgb(12, 100, 192);">-eps_nev 10 -eps_ncv 140 -eps_target 0.0+0.0i -st_type sinvert</span><br>
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-in this case the code crashed at the point it tried to call slepc, so perhaps I have incorrectly specified these options ?<br>
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Does anyone have any suggestions as to how to improve this performance ( or find out more about the problem) ?</div>
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In the case of A) I can see from watching the slepc videos that increasing ncv <br>
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may help, but I am wondering , since 600 is a large number of iterations, whether there
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maybe something else going on - e.g. perhaps some alternative preconditioner may help ?</div>
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In the case of B), I guess there must be some mistake in these command line options?</div>
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Again, any advice will be greatly appreciated.</div>
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Best wishes, Dan.<br>
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