[Octave-bug-tracker] [bug #42097] 64bit Slackware, eig returning incorrect results

[Jordi Gutiérrez Hermoso]

Follow-up Comment #6, bug #42097 (project octave):

Something is awfully wrong on your side. These are my results:


octave:7> A = [0 1 0; 0 0 1; 1 0 0]
A =

   0   1   0
   0   0   1
   1   0   0

octave:8> format long
octave:9> [V, D] = eig(A)
V =

   0.577350269189626 + 0.000000000000000i   0.577350269189626 -
0.000000000000000i  -0.577350269189626 + 0.000000000000000i
  -0.288675134594813 + 0.500000000000000i  -0.288675134594813 -
0.500000000000000i  -0.577350269189626 + 0.000000000000000i
  -0.288675134594813 - 0.500000000000000i  -0.288675134594813 +
0.500000000000000i  -0.577350269189626 + 0.000000000000000i

D =

Diagonal Matrix

  -0.500000000000000 + 0.866025403784439i                                     
  0                                        0
                                        0  -0.500000000000000 -
0.866025403784439i                                        0
                                        0                                     
  0   1.000000000000000 + 0.000000000000000i

octave:10> A*V -V*D
ans =

  -5.55111512312578e-17 - 6.10622663543836e-16i  -5.55111512312578e-17 +
6.10622663543836e-16i  -1.11022302462516e-16 + 0.00000000000000e+00i
  -1.11022302462516e-16 + 2.22044604925031e-16i  -1.11022302462516e-16 -
2.22044604925031e-16i  -4.44089209850063e-16 + 0.00000000000000e+00i
   2.22044604925031e-16 + 1.11022302462516e-16i   2.22044604925031e-16 -
1.11022302462516e-16i   2.22044604925031e-16 + 0.00000000000000e+00i


How did you compile Octave? Which implementation of LAPACK are you using?

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