Repair _check_homomorphism()

[skieffer]

References to other Issues or PRs

Fixes #24442

Release Notes

• combinatorics
  • Fix a bug in forming a group homomorphism with PermutationGroup as domain. Previously this would raise ValueError incorrectly in some cases.

[sympy-bot]

✅

Hi, I am the SymPy bot (v169). I'm here to help you write a release notes entry. Please read the guide on how to write release notes.

Your release notes are in good order.

Here is what the release notes will look like:

• combinatorics
  • Fix a bug in forming a group homomorphism with PermutationGroup as domain. Previously this would raise ValueError incorrectly in some cases. (#24443 by @skieffer)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.12.

Click here to see the pull request description that was parsed.

<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->

#### References to other Issues or PRs
<!-- If this pull request fixes an issue, write "Fixes #NNNN" in that exact
format, e.g. "Fixes #1234" (see
https://tinyurl.com/auto-closing for more information). Also, please
write a comment on that issue linking back to this pull request once it is
open. -->

Fixes #24442 

#### Release Notes

<!-- Write the release notes for this release below between the BEGIN and END
statements. The basic format is a bulleted list with the name of the subpackage
and the release note for this PR. For example:

* solvers
  * Added a new solver for logarithmic equations.

* functions
  * Fixed a bug with log of integers.

or if no release note(s) should be included use:

NO ENTRY

See https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more
information on how to write release notes. The bot will check your release
notes automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
* combinatorics
  * Fix a bug in forming a group homomorphism with PermutationGroup as domain. Previously this would raise ValueError incorrectly in some cases.
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[github-actions]

Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)

Significantly changed benchmark results (master vs previous release)

       before           after         ratio
     [41d90958]       [809c53c0]
     <sympy-1.11.1^0>                 
-     1.10±0.02ms         680±10μs     0.62  solve.TimeSparseSystem.time_linear_eq_to_matrix(10)
-      3.04±0.1ms      1.22±0.05ms     0.40  solve.TimeSparseSystem.time_linear_eq_to_matrix(20)
-      6.13±0.2ms      1.88±0.03ms     0.31  solve.TimeSparseSystem.time_linear_eq_to_matrix(30)

Full benchmark results can be found as artifacts in GitHub Actions
(click on checks at the top of the PR).

[oscarbenjamin]

combinatorics

• Fix a bug in homomorphisms

The release note should clarify a bit more what is changed or what the bug is.

[skieffer]

I edited the release note. Don't know if sympy-bot sends another email in response to the edit.

[oscarbenjamin]

I've added a bit more to it. For someone reading the release note a "bug" can mean many different things. Did the operation previously give mathematically incorrect results or did it just crash? Was it wrong in all cases or only some?

[skieffer]

Sure, that can be helpful.

Maybe we should update the PR template. Currently, it only gives this as an example of a release note relating to a bug:

* functions
  * Fixed a bug with log of integers.

[oscarbenjamin]

Yeah, I suppose that giving an actually reasonable example in the template is probably a good idea!