Determinant and inverse calculation is wrong

[Sameer Grover]

I have a complex 2X2 matrix for which I'd like to calculate the determinant.  mpmath's det function gives a determinant of zero even though the matrix is non-singular.

We can get the correct value by multiplying term-by-term. Consider the code:

#========================
from __future__ import division
import numpy as np
import mpmath

m3 = np.matrix([[  5.18895807e-12 +0.00000000e+00j,
           1.92716917e+11 +0.00000000e+00j],
        [  0.00000000e+00 -1.93643371e-11j,
           0.00000000e+00 -5.16413237e+10j]])
m = mpmath.matrix(m3)
print np.linalg.det(m3)
print mpmath.det(m)
print m[0,0]*m[1,1]- m[1,0]*m[0,1]
#======================== 

The output is :
3.4638706823j
0
(0.0 + 3.46387068230212j)

mpmath's det function gives a determinant of zero even though the matrix is non-singular. We get the correct value by multiplying term-by-term. This happens for any value of the precision.
 Can somebody confirm this bug?

I have made a bug report (Issue#229).  

Thank you.

Regards,
Sameer

[Fredrik Johansson]

Hi Sameer,

Yep. Definitely a problem with the way LU_decomp detects matrices
being singular.

> I have made a bug report (Issue#229).

Thanks.

Fredrik

[Sameer Grover]

Thanks for the confirmation.

Sameer