Macaulay2 / Macaulay2/M2

bug in rawGCDRingElement

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Core Engine
Dominant language
Macaulay2
Stars
435
Forks
297
Avg merge
4d 20h
Merged PRs (30d)
11

Description

This bug has haunted a number of things related to LocalRings over QQ forever:
```m2
i1 : R = QQ; gcd(2_R, 8_R)

o2 = 2

o2 : QQ

i3 : R = QQ[x]; gcd(2_R, 8_R)

o4 = 1

o4 : R
```
You can try calling `showcf` to get the values of these three to see where this is happening:
https://github.com/Macaulay2/M2/blob/deb37e0a86df12c65ea1cdb7a83d960e7c1c06f7/M2/Macaulay2/e/interface/factory.cpp#L524-L526

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the two gcd examples in Macaulay2 and use showcf on the resulting values. Start at M2/Macaulay2/e/interface/factory.cpp lines 524-526 and trace rawGCDRingElement; done means the examples return 2 over QQ and 1 over QQ[x] without the reported inconsistency.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
backend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
52/100

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