[petsc-users] SLEPC - Hermitian matrix gives complex eigenvalues

[Pandey, Siddhant]

Hello all,

I am diagonalizing a hermitian matrix (MatIsHermitian = 1 up to a tolerance of 1e-15) using krylovschur, with EPS_TARGET_MAGNITUDE = 0, but getting complex eigenvalues. Also, I am getting seemingly spurious eigenvalues of magnitude very close to 0, whose relative errors are much larger than my set tolerance. Can anyone indicate what might be the cause and possible solutions.

I have attached the files eps_view, A_mat_binary, and B_mat_binary files, which show the settings I have used, and contain the A and B matrices respectively (in binary).

The eigenvalues I get are:

  #                    Eigenvalue
 —      ----------------------------------------------------------------
  0         0.0000000000000077  + i -0.0000000000000000
  1         0.0000000000000265  + i -0.0000000000000008
  2         0.0000000000000340  + i 0.0000000000000002
  3         0.0000000000000373  + i 0.0000000000000001
  4         0.0000000000000444  + i -0.0000000000000007
  5         0.0000000000000448  + i -0.0000000000000017
  6         0.0000000000000470  + i 0.0000000000000002
  7         0.0000000000000489  + i 0.0000000000000030
  8         0.0000000000000548  + i 0.0000000000000006
  9         0.0000000000000585  + i 0.0000000000000001
  10       0.0000000000000643  + i 0.0000000000000005
  11       0.0000000000000714  + i -0.0000000000000008
  12       0.0000000000000750  + i -0.0000000000000019
  13       0.0000000000000752  + i 0.0000000000000031
  14       0.0000000000000769  + i -0.0000000000000002
  15       0.0000000000000784  + i -0.0000000000000037
  16       0.0000000000000860  + i 0.0000000000000002
  17       0.0000000000000880  + i -0.0000000000000004
  18       0.0000000000000968  + i -0.0000000000000001
  19       0.0000000000000979  + i 0.0000000000000013
  20       0.0000000000001045  + i -0.0000000000000001
  21       0.0000000000001150  + i -0.0000000000000011
  22       0.0000000000001348  + i -0.0000000000000012
  23       0.0000000000001446  + i -0.0000000000000019
  24       0.0000000000001454  + i 0.0000000000000011
  25       0.0000000000001555  + i 0.0000000000000003
  26       0.0000000000002513  + i -0.0000000000000009
  27       5.0908854514230413  + i -0.0022004178122762
  28       5.2768106039842175  + i 0.1043464906789375
  29       5.3003883062604187  + i -0.0757735907905433
  30       11.5143655883932929 + i 0.0049838692042474
  31       11.8821523259838653 + i -0.1475608751440501
  32       11.9515216995487101 + i 0.1857395729336506
  33       12.0909362158339384 + i 0.0049114285397287
  34       12.0905704159492675 + i -0.1522880348537981
  35       12.2205398661469111 + i -0.0781999802933937
  36       12.4807156964720480 + i -0.2850122604907908
  37       12.6082849940660289 + i 0.0560456679728079
  38       12.9384278480576125 + i 0.0238826907631012
  39       17.5230234731441357 + i -0.1824807274488794
  40       17.5503678395543901 + i 0.1785356473404145
  41       17.6933953160112409 + i -0.0626631055149425
  42       19.1692824404480930 + i -0.6351729266691462
  43       19.4158452684509797 + i 0.3151965488807310
  44       19.6020750507704591 + i -0.2559887580276014
  45       19.6443102906562181 + i 1.1005601705485646
  46       19.7948713379697452 + i 0.1230015140422697
  47       19.8791098474284347 + i -0.1943322911563744
  48       20.1268732265661860 + i -0.0340890856219265
  49       20.1368588182453898 + i 0.2673370459460956


Thanks in advance,
Sidd
Worcester Polytechnic, U.S.A.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20170913/6443517a/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: A_mat_binary
Type: application/octet-stream
Size: 2816632 bytes
Desc: A_mat_binary
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20170913/6443517a/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: B_mat_binary
Type: application/octet-stream
Size: 2816632 bytes
Desc: B_mat_binary
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20170913/6443517a/attachment-0003.obj>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: eps_view_pre.txt
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20170913/6443517a/attachment-0001.txt>