#8977: Bug in QuadraticForm.rational_diagonal_form()
-------------------------------+--------------------------------------------
Reporter: gdrama | Owner: justin
Type: defect | Status: new
Priority: minor | Milestone:
Component: quadratic forms | Keywords: rational_diagonal_form()
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
-------------------------------+--------------------------------------------
The function rational_diagonal_form() fails in some quadratic forms. For
example:
{{{
sage: Q = QuadraticForm(ZZ,2,[0,1,-1])
sage: Q
Quadratic form in 2 variables over Integer Ring with coefficients:
[ 0 1 ]
[ * -1 ]
sage: Q.rational_diagonal_form()
---------------------------------------------------------------------------
ZeroDivisionError Traceback (most recent call
last)
/home/gustavo/<ipython console> in <module>()
/home/gustavo/sage-4.3.3/local/lib/python2.6/site-
packages/sage/quadratic_forms/quadratic_form__local_field_invariants.pyc
in rational_diagonal_form(self, return_matrix)
113 for j in range(i+1, n):
114 if Q[i,j] != 0:
--> 115 temp[i,j] = -Q[i,j] / (Q[i,i] * 2) ## This
should only occur when Q[i,i] != 0, which the above step guarantees.
116
117 Q = Q(temp)
/home/gustavo/sage-4.3.3/local/lib/python2.6/site-
packages/sage/structure/element.so in
sage.structure.element.RingElement.__div__
(sage/structure/element.c:11882)()
/home/gustavo/sage-4.3.3/local/lib/python2.6/site-
packages/sage/rings/rational.so in sage.rings.rational.Rational._div_
(sage/rings/rational.c:14641)()
ZeroDivisionError: Rational division by zero
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8977>
Sage <http://www.sagemath.org>
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