From: Ondrej Certik <ondrej@ce...>  20060116 09:35:16

Hi, I also use the generalized eigenvalue problem and it works fine. Many thanks. I have a question: I have a real symmetric problem, so I get only r= eal eigenvalues, but I need to get the lowest ones. So I use: eigen_system.eigen_solver>set_position_of_spectrum(SMALLEST_MAGNITUDE); The problem is, that all the solvers from slepc package (ARNOLDI, SUBSPACE, POWER) don't support the "SMALLEST_MAGNITUDE" option, see their sources, for example slepc2.3.0/src/eps/impls/arnoldi/arnoldi.c, line 38: if (eps>which!=3DEPS_LARGEST_MAGNITUDE) SETERRQ(1,"Wrong value of eps>which"); Except the "LAPACK" solver. Lapack works fine, but it retrieves all the eigenvalues and is really slow, in fact for a bigger mesh it's completely unusable (but works). Is there a way how to get the lowest eigenvalues with slepc (maybe using some trick)? In the meantime, I export the element matrices to a file and use external solver, pysparse http://people.web.psi.ch/geus/pyfemax/pysparse.html so I have a small (88 lines) python script, which assembles the global matr= ices (they are called A and B in libmesh), and calls Jacobi Davidson method from pysparse module. The solver is written in C (exported to python), it's fast= and it works.=20 Ondrej On Mon, Jan 16, 2006 at 12:25:50AM +0100, Steffen Petersen wrote: > Hello Michael, >=20 > a few weeks ago you have asked for > solving generalized eigenvalue problems with libMesh. > Meanwhile, I have extended the slepc interface > to also support generalized problems > (with a few modifaications example 16 > may be used for solving a generalized eigenvalue > problem). > Feel free to ask if you are interested in some > more details. >=20 > Steffen >=20 >=20 >=20 > Michael Povolotskyi schrieb: > >Dear Libmesh developers, > >I have to solve an eigenvalue problem for a quantum physics calculations. > >My questions are: > >1) Is it possible to solve a general eigenvalue problem like Hx =3D Sx,= =20 > >where H and S are known matrixes. > >2) Is it possible to have complex (selfconjugated) matrixes? > > > >Thank you, > >Michael. > >=20 > > This SF.net=20 > >email is sponsored by: Splunk Inc. Do you grep through log files for=20 > >problems? Stop! Download the new AJAX search engine that makes searching= =20 > >your log files as easy as surfing the web. DOWNLOAD SPLUNK!=20 > >http://ads.osdn.com/?ad_idv37&alloc_id=16865&op=3Dclick=20 > >_______________________________________________ Libmeshusers mailing=20 > >list Libmeshusers@...=20 > >https://lists.sourceforge.net/lists/listinfo/libmeshusers >=20 >=20 >=20 >  > This SF.net email is sponsored by: Splunk Inc. Do you grep through log fi= les > for problems? Stop! Download the new AJAX search engine that makes > searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! > http://ads.osdn.com/?ad_id=3D7637&alloc_id=3D16865&op=3Dclick > _______________________________________________ > Libmeshusers mailing list > Libmeshusers@... > https://lists.sourceforge.net/lists/listinfo/libmeshusers 