Implementing DigraphEdgeConnectivity

[RheyaM]

Implemented two methods for calculating the EdgeConnectivity of a Digraph, one using Spanning Trees and one using Dominating Sets, based on the Algorithms detailed in: https://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf

Additional functions: DigraphDominatingSet() and DigraphGetNeighbourhood(), for getting a Dominating Set of a digraph and getting the neighbourhood of a subset of vertices in a digraph, respectively.

[reiniscirpons]

Thanks for the implementation! I had some suggestions for the documentation and for improving the performance of the methods. Mainly more details in the docs and reworking some loops to implement more efficient DFS.

Some other things:

• The documentation is not currently linked in the manual. You should edit the correct doc/z-chapX.xml file to add this. For example, to get the DigraphDominatingSet documentation to show up you should add the <#Include Label="DigraphDominatingSet"> tag in the correct place of doc/z-chap4.xml. You can test this by seeing if ?DigraphDominatingSet shows up the docs after running DigraphsMakeDoc() in gap. Same applies for the other functions.
• Functions need to be more careful about symmetric vs non symmetric digraphs.
• You should re-run the benchmarks after making the performance based changes to the implementation. I think currently the benchmarks are skewed by the time it takes to find the dominating set/spanning tree, but after the reimplementation this time should become negligible, and it will be more about how many vertices need to be checked. So maybe hold-off on removing the methods for now.

Afterwards should be good to merge!

[mtorpey]

@RheyaM, I wonder if you could merge or rebase to resolve the merge conflicts with the current main branch. Then could you indicate whether you think you've resolved @reiniscirpons's comments? We can then review this again.

[reiniscirpons]

Thanks again for the PR @RheyaM ! I took some time to finish off some minor polish so we can merge into main.

@mtorpey @james-d-mitchell Could either of you give this a review when you have the time please?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.47%. Comparing base (c4ced48) to head (c3f4897).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #884      +/-   ##
==========================================
+ Coverage   97.46%   97.47%   +0.01%     
==========================================
  Files          51       51              
  Lines       21191    21301     +110     
  Branches      639      639              
==========================================
+ Hits        20653    20763     +110     
  Misses        473      473              
  Partials       65       65              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

Resolved

[james-d-mitchell]

Some superficial changes, then I'm happy to merge this

[reiniscirpons]

@james-d-mitchell ready for re-review

[james-d-mitchell]

Thanks @RheyaM and @reiniscirpons !