#12292: charpoly is recomputed when called with a different variable
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Reporter: zimmerma | Owner: jason, was
Type: enhancement | Status: needs_review
Priority: minor | Milestone: sage-5.0
Component: linear algebra | Resolution:
Keywords: sd35.5 | Work issues:
Report Upstream: N/A | Reviewers: Paul Zimmermann
Authors: Michael Orlitzky | Merged in:
Dependencies: | Stopgaps:
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Comment (by zimmerma):
I agree with item 1 from comment [comment:6], but in Sage 4.8:
{{{
sage: A = random_matrix(QQ, 3)
sage: A.charpoly()
x^3 + x^2 + 5/4*x + 1/2
sage: A._cache
{'clear_denom': ([-1 2 0]
[-2 0 0]
[ 0 -1 -1], 2), 'charpoly_linbox_x': x^3 + x^2 + 5/4*x + 1/2}
sage: A.charpoly('t')
t^3 + t^2 + 5/4*t + 1/2
sage: A._cache
{'clear_denom': ([-1 2 0]
[-2 0 0]
[ 0 -1 -1], 2), 'charpoly_linbox_x': x^3 + x^2 + 5/4*x + 1/2,
'charpoly_linbox_t': t^3 + t^2 + 5/4*t + 1/2}
}}}
thus calling {{{A._cache['charpoly_linbox']}}} might not be enough.
Paul Zimmermann
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12292#comment:7>
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