Macaulay2 / Macaulay2/M2

Bug in rawSelectByDegrees

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Engine
Dominant language
Macaulay2
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Merged PRs (30d)
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Description

What is happening here?
```m2
R = ZZ/101[a..d, Degrees=>toList(4:{1,2})]
M = coker matrix"a,b;c,d"
SM = symmetricAlgebra M
debug Core
A = raw source matrix {{p_0, p_1}}
tally apply(100, i -> rawSelectByDegrees(A, {1}, {1}))
tally apply(100, i -> rawSelectByDegrees(A, {1}, {1,0,0}))
```

Example:
```m2
i18 : tally apply(100, i -> rawSelectByDegrees(A, {0}, {1,0,0}))

o18 = Tally{{} => 42 }
{0, 1} => 58
```
The input isn't valid, but absent of an error, the output is bizarre.

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  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 examples in the issue, starting with the rawSelectByDegrees calls on the raw source matrix A. Locate the implementation or entry point for rawSelectByDegrees and trace how invalid degree inputs are handled. Done means the invalid input has defined, non-bizarre behavior, preferably with a regression check for the shown cases.

Written by the indexing model from the issue text.

Assessment

Domain
tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
45/100

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