#5208: Differing behavior for matrix left_kernel vs. right_kernel
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Reporter: rbeezer | Owner: rbeezer
Type: defect | Status: new
Priority: minor | Milestone: sage-3.4.1
Component: linear algebra | Keywords: matrix, left_kernel, right_kernel
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Calls to left_kernel() don't properly filter down the class hierarchy for
matrices, and so do not always use the most efficient algorithm available.
The transcript below illustrates the difference in time for a
mathematically equivalent computation on a random 200 x 200 matrix of two-
digit integers.
{{{
sage: a = random_matrix(ZZ, 200, 200, x=100).change_ring(QQ)
sage: time a.transpose().right_kernel()
Vector space of degree 200 and dimension 0 over Rational Field
Basis matrix:
0 x 200 dense matrix over Rational Field
Time: CPU 0.18 s, Wall: 0.18 s
sage: time a.left_kernel()
Vector space of degree 200 and dimension 0 over Rational Field
Basis matrix:
0 x 200 dense matrix over Rational Field
CPU time: 70.76 s, Wall time: 71.55 s
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5208>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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