Opened 6 years ago

Last modified 3 years ago

## #18787 closed defect

# Bug with matrice products over Symbolic Ring with modular integers — at Initial Version

Reported by: | tmonteil | Owned by: | |
---|---|---|---|

Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |

Component: | symbolics | Keywords: | |

Cc: | kcrisman, slelievre | Merged in: | |

Authors: | Reviewers: | ||

Report Upstream: | N/A | Work issues: | |

Branch: | Commit: | ||

Dependencies: | Stopgaps: |

### Description

As reported on 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]

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