I use EPS_GHEP and PetscScalar is complex. I am wondering why i see this result. You can see from the eigenvectors in the previous email that the magnitudes of the components match. For the lapack/matlab solution the phase is pi (180 degres) for each component where as for defualt or arpack method phase is 56.53 degrees for each component. I will prepare a test case and email the code.
thanks Reddy On Tue, Jan 3, 2012 at 1:59 AM, Jose E. Roman <jroman at dsic.upv.es> wrote: > > On 03/01/2012, Dharmendar Reddy wrote: > > > Hello, > > I have a query regarding the eigenvectors computed in slepc. I > am solving a genralized eigenvalue problem. I have attached the A and B > matrices with this email. If i run slepc solver with default options are > arpack, i get one set of vectors (complex) as solution. If i run with > eps_type lapack I get real vectors. A is hermitian, and B is positive > definite. ( the actual problem is a schrodinger equation for particle in > infinite potential well, so the solution will be of the form sin(x)). I > check the solution in matlab using eig(A,B) i get real vectors. Looks like > there is some unitary transformation involved here, can you tell me what > could be going on. > > > > i copy a small portion of the eigen vector of the lowest magnitude > eigenvlaue (=0.0887) > > ---Method: (slepc and eps_type lapack) or matlab----- > > (-0.101596582735892,0.000000000000000E+000) > > (-0.200421875537261,0.000000000000000E+000) > > (-0.293780182034781,0.000000000000000E+000) > > (-0.379124930994127,0.000000000000000E+000) > > ... > > ... > > ... > > (-0.293780182033444,0.000000000000000E+000) > > (-0.200421875536298,0.000000000000000E+000) > > (-0.101596582735387,0.000000000000000E+000) > > > ------------------------------------------------------------------------------ > > ---Method: (slepc and eps_type defualt or arpack) ---- > > > > > > (5.602609025416389E-002,8.475224384072830E-002) > > (0.110523934800485,0.167192667375096) > (0.162006974547097,0.245072510835553) > > (0.209070886310831,0.316267414979582) > (0.250431889351034,0.378835368586700) > > (0.284961763219882,0.431069680779720) > (0.311718623092706,0.471545535910556) > > (0.329972611445050,0.499158857936955) > (0.339225807211469,0.513156427631836) > > (0.339225807166595,0.513156427588630) > (0.329972611486755,0.499158857980068) > > (0.311718623054404,0.471545535864886) > (0.284961763251251,0.431069680822535) > > (0.250431889322221,0.378835368543795) > (0.209070886332945,0.316267415014661) > > (0.162006974528570,0.245072510805346) > (0.110523934811968,0.167192667394530) > > (5.602609024797538E-002,8.475224382992022E-002) > > I cannot reproduce the problem. I always get the correct eigenvector. Are > you doing the computation in real arithmetic? Are you setting the problem > type to EPS_GHEP? > > Jose > > > > -- ----------------------------------------------------- Dharmendar Reddy Palle Graduate Student Microelectronics Research center, University of Texas at Austin, 10100 Burnet Road, Bldg. 160 MER 2.608F, TX 78758-4445 e-mail: dharmareddy84 at gmail.com Phone: +1-512-350-9082 United States of America. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120103/eefca335/attachment-0001.htm>
