Opened 5 years ago

Closed 5 years ago

## #24424 closed defect (fixed)

# Dancing links random failures

Reported by: | Volker Braun | Owned by: | |
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Priority: | major | Milestone: | sage-8.2 |

Component: | combinatorics | Keywords: | random_fail |

Cc: | Sébastien Labbé, Vincent Delecroix | Merged in: | |

Authors: | Sébastien Labbé | Reviewers: | Volker Braun |

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

Branch: | 2df8c97 (Commits, GitHub, GitLab) | Commit: | 2df8c973e4b7f0c0ced1d45ecf3f2a273d971892 |

Dependencies: | Stopgaps: |

### Description

The output of `one_solution`

is random:

********************************************************************** File "src/sage/combinat/matrices/dancing_links.pyx", line 27, in sage.combinat.matrices.dancing_links Failed example: sorted(x.one_solution(ncpus=8)) Expected: [0, 1] Got: [2, 3] ********************************************************************** 1 item had failures: 1 of 20 in sage.combinat.matrices.dancing_links [175 tests, 1 failure, 8.38 s] ---------------------------------------------------------------------- sage -t --long src/sage/combinat/matrices/dancing_links.pyx # 1 doctest failed ----------------------------------------------------------------------

Also, does ncpus=8 really use 8 cores? We already parallelize doctests! Tests should definitely not x8 that.

### Change History (6)

### comment:1 Changed 5 years ago by

Branch: | → u/slabbe/24424 |
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Commit: | → 2df8c973e4b7f0c0ced1d45ecf3f2a273d971892 |

### comment:2 Changed 5 years ago by

Status: | new → needs_review |
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### comment:3 Changed 5 years ago by

Replying to vbraun:

Also, does ncpus=8 really use 8 cores? We already parallelize doctests! Tests should definitely not x8 that.

I changed 8 to 2. The dancing links problem in question uses only 6 rows. So, it is not something that will use a lot of cpu time (something like 1ms).

### comment:4 Changed 5 years ago by

Reviewers: | → Volker Braun |
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Status: | needs_review → positive_review |

### comment:5 Changed 5 years ago by

Authors: | → Sébastien Labbé |
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### comment:6 Changed 5 years ago by

Branch: | u/slabbe/24424 → 2df8c973e4b7f0c0ced1d45ecf3f2a273d971892 |
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Resolution: | → fixed |

Status: | positive_review → closed |

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New commits:

`24424: fixing random doctests failures`