#18787: Bug with matrice products over Symbolic Ring with modular integers
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Reporter: tmonteil | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.8
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by jdemeyer:
Old description:
> As reported on [http://ask.sagemath.org/question/27196/multiplying-
> matrices-with-different-parents/ this ask question]
>
> {{{
> sage: sage: var('A,B,C,D')
> (A, B, C, D)
> sage: S = matrix(SR,2,[[1+3*A,3*B],[3*C,1+3*D]])
> sage: R = Zmod(9)
> sage: g = matrix(R,2,[[2,1],[2,6]])
> sage: gi = matrix(R,2,[[6,8],[7,2]])
> sage: g*S*gi
> [ 6*B + 3*D + 1 3*A + 3*B + 6*C + 6*D]
> [ 0*A + 0*D 3*A + 0*D + 1]
> }}}
>
> While we have (look at the second line):
>
> {{{
> sage: R.<A,B,C,D> = PolynomialRing(Zmod(9),4)
> sage: g = matrix(R,2,[[2,1],[2,6]])
> sage: gi = matrix(R,2,[[6,8],[7,2]])
> sage: S = matrix(R,2,[[1+3*A,3*B],[3*C,1+3*D]])
> sage: g*S*gi
> [ 6*B + 3*D + 1 3*A + 3*B + 6*C + 6*D]
> [ 6*B 3*A + 3*B + 1]
> }}}
New description:
As reported on [http://ask.sagemath.org/question/27196/multiplying-
matrices-with-different-parents/ this ask question]
{{{
sage: _ =var('A,B,C,D')
sage: S = matrix([[1+3*A,3*B],[3*C,1+3*D]])
sage: R = Zmod(9)
sage: g = matrix(R,2,[[2,1],[2,6]])
sage: gi = matrix(R,2,[[6,8],[7,2]])
sage: g*S*gi
[ 6*B + 3*D + 1 3*A + 3*B + 6*C + 6*D]
[ 0*A + 0*D 3*A + 0*D + 1]
}}}
While we have (look at the second line):
{{{
sage: P.<A,B,C,D> = ZZ[]
sage: S = matrix([[1+3*A,3*B],[3*C,1+3*D]])
sage: R = Zmod(9)
sage: g = matrix(R,2,[[2,1],[2,6]])
sage: gi = matrix(R,2,[[6,8],[7,2]])
sage: g*S*gi
[ 6*B + 3*D + 1 3*A + 3*B + 6*C + 6*D]
[ 6*B 3*A + 3*B + 1]
}}}
--
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Ticket URL: <http://trac.sagemath.org/ticket/18787#comment:1>
Sage <http://www.sagemath.org>
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