#5144: [with patch, needs review] speed up right_nullity for matrices
----------------------------+-----------------------------------------------
Reporter: jhpalmieri | Owner: was
Type: defect | Status: new
Priority: minor | Milestone: sage-3.3
Component: linear algebra | Keywords: right_nullity
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left_nullity currently functions by computing the difference between
self.nrows() and self.rank().
right_nullity currently functions by calling left_nullity on the transpose
of the matrix, and so it can be sped up if it instead computes
self.ncols() - self.rank(). The attached patch does this.
To see the effect, try timing some things with
{{{
sage: m = random_matrix(ZZ, 50, x=2^16)
}}}
On my machine, I get
{{{
sage: timeit('m.left_nullity()')
625 loops, best of 3: 2.29 µs per loop
timeit('m.transpose()')
125 loops, best of 3: 1.72 ms per loop
}}}
so the transpose operation is really slow.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5144>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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