Macaulay2 / Macaulay2/M2

lyubeznikResolution bug

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package issue
Dominant language
Macaulay2
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435
Forks
297
Avg merge
4d 20h
Merged PRs (30d)
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Description

In the simplicial Complexes package if the `lyubeznikResolution` function is passed a `monomialIdeal` that has 6 or more minimal generators an index error occurs. It seems the issue stems from the following lines in M2/Macaulay2/packages/SimplicialComplexes/Code.m2

```
841 MinGens := flatten entries mingens I;
842 MO := opts.MonomialOrder;
843 R := QQ(monoid[vars(0..#(mingens I)-1)]);
```
In the last line # is applied to the matrix `mingens I`. This always returns 5, the number of keys in the dictionary used to store matrices. This can be fixed by replacing line 843 with `R := QQ(monoid[vars(0..#(MinGens)-1)]); ` which instead uses the local variable `MinGens`.

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First steps

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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

Open M2/Macaulay2/packages/SimplicialComplexes/Code.m2 and inspect lines 841–843, especially how the minimal generators are counted. Reproduce the issue with a monomialIdeal having six or more minimal generators, then verify that the index error no longer occurs after the count uses MinGens.

Written by the indexing model from the issue text.

Assessment

Domain
tooling
Issue type
Bug
Difficulty
1/5
Estimated time
Under an hour
Activity status
Active
Clarity
Clearly specified
Newbie friendliness
82/100

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