Re: Issues with eigs

[Thomas D. Dean]

There is a problem here.  I know about roundoff error, etc.  Even with 
roundoff error, I believe I should get the same result every time I run 
this.

octave:722> eigs(m1,m0)
ans =

         0.00026 - 2672325.75636i
         0.00026 + 2672325.75636i
         0.00000 + 2639890.67488i
         0.00000 - 2639890.67488i
        -0.00007 - 2587678.50828i
        -0.00007 + 2587678.50828i

octave:723> eigs(m1,m0)
ans =

         0.00050 - 2672274.01721i
         0.00050 + 2672274.01721i
        -0.00058 + 2639991.91956i
        -0.00058 - 2639991.91956i
        -0.00005 - 2587660.78340i
        -0.00005 + 2587660.78340i

octave:724> eigs(m1,m0)
ans =

         0.00014 + 2672332.27197i
         0.00014 - 2672332.27197i
        -0.00030 - 2639921.38497i
        -0.00030 + 2639921.38497i
         0.00001 - 2587707.77163i
         0.00001 + 2587707.77163i

With Scipy, I get the same result every time I run it.  I verified that 
both octave and numpy read the matrix the same way - non-zero values are 
the same and in the same location.

#!/usr/bin/python3

import numpy as np
from scipy import linalg as la

m0 = np.loadtxt('/tmp/M0.txt')
m1 = np.loadtxt('/tmp/M1.txt')

e1, w1 = la.eig(m0, m1)
e2, w2 = la.eig(m0, m1)
for idx in range(len(e1)):
    if e1[idx] != e2[idx]:
        print(e1[idx], ' != ', e2[idx])

Tom Dean