[petsc-users] slepc eigenvectors

[Dharmendar Reddy]

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)





-- 
-----------------------------------------------------
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.
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