Opened 8 months ago

Closed 8 months ago

## #33902 closed defect (duplicate)

# bug in 'tedder' modular decomposition

Reported by: | dimpase | Owned by: | |
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Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |

Component: | graph theory | Keywords: | |

Cc: | dcoudert | Merged in: | |

Authors: | Reviewers: | Dima Pasechnik | |

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

Branch: | Commit: | ||

Dependencies: | Stopgaps: |

### Description (last modified by )

in #26496 a simple implementation of modular decomposition was added, but no explicit example showing that 'tedder' is buggy. (PS - but see #25872) An example is now posted on sage-devel:

sage: d = { ....: 1 : [2, 3, 4], ....: 2 : [1, 3, 4], ....: 3 : [1, 2, 4], ....: 4 : [1, 2, 3, 5], ....: 5 : [10, 4, 6, 7, 8, 9], ....: 6 : [5, 7], ....: 7 : [5, 6, 8, 9], ....: 8 : [5, 7, 9], ....: 9 : [10, 5, 7, 8], ....: 10 : [5, 9] ....: } ....: g = Graph(d) sage: g.modular_decomposition(algorithm='tedder') # --- wrong ?! (PRIME, [5, (SERIES, [9, (PARALLEL, [10, 7, 8, 6])]), 4, (SERIES, [3, 2, 1])]) sage: g.modular_decomposition(algorithm='habib') (PRIME, [5, 4, (SERIES, [1, 2, 3]), (PRIME, [9, 7, 6, 8, 10])])

### Change History (5)

### comment:1 Changed 8 months ago by

Description: | modified (diff) |
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### comment:2 Changed 8 months ago by

### comment:3 Changed 8 months ago by

Milestone: | sage-9.7 → sage-duplicate/invalid/wontfix |
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Status: | new → needs_review |

will be fixed in #25872

### comment:4 Changed 8 months ago by

Reviewers: | → Dima Pasechnik |
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Status: | needs_review → positive_review |

### comment:5 Changed 8 months ago by

Resolution: | → duplicate |
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Status: | positive_review → closed |

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Since we remove algorithm

`'tedder'`

in #25872, we can move this ticket to`wontfix`

.