#13661: accuracy problem in matrix_mod_pn for Eisenstein extensions of padics
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Reporter: saraedum | Owner: roed
Type: enhancement | Status: new
Priority: minor | Milestone: sage-5.5
Component: padics | Keywords:
Work issues: | Report Upstream: N/A
Reviewers: | Authors: Julian Rueth
Merged in: | Dependencies: #13659
Stopgaps: |
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Currently, the accuracy of the matrix returned by {{{matrix_mod_pn()}}} in
padic extension rings is probably too small:
{{{
sage: R=ZpCA(3,5)
sage: S.<a> = R[]
sage: L.<a>=R.extension(a^2-3)
sage: t=a.add_bigoh(2)
sage: t.matrix_mod_pn()
[0 1]
[0 0]
sage: (t*a)._ntl_rep_abs() # but t*a is not zero
([3], 0)
}}}
I think it would be better to return the following:
{{{
[0 1]
[3 0]
}}}
Of course, the "1" is not known to precision {{{O(3^2)}}} but I think it
is better to leave it to the caller to strip away the digits that are not
wanted.
The attached patch increases the precision to the maximal precision of any
of the entries of the matrix.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13661>
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