#4502: numerical noise in matrix_double_dense on intel mac os X 10.5: inverting
a
singular matrix
----------------------------+-----------------------------------------------
Reporter: jhpalmieri | Owner: somebody
Type: defect | Status: new
Priority: major | Milestone: sage-3.2
Component: linear algebra | Keywords: numerical noise, matrix
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(This has only been reported on intel macs running 10.4 or 10.5.)
From [http://groups.google.com/group/sage-
devel/browse_frm/thread/fae59a9a9a53b8c0 sage-devel]:
{{{
sage: A = matrix(RDF,3,range(1,10));A
[1.0 2.0 3.0]
[4.0 5.0 6.0]
[7.0 8.0 9.0]
sage: A.determinant()
0.0
sage: -A
[-1.0 -2.0 -3.0]
[-4.0 -5.0 -6.0]
[-7.0 -8.0 -9.0]
sage: b = A.numpy(); b
array([[ 1., 2., 3.],
[ 4., 5., 6.],
[ 7., 8., 9.]])
sage: import scipy
sage: import scipy.linalg
sage: scipy.linalg.det(b)
0.0
sage: scipy.linalg.inv(b)
array([[ -4.50359963e+15, 9.00719925e+15, -4.50359963e+15],
[ 9.00719925e+15, -1.80143985e+16, 9.00719925e+15],
[ -4.50359963e+15, 9.00719925e+15, -4.50359963e+15]])
}}}
This leads to a doctest failure for {{{matrix_double_dense.py}}}.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4502>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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