1.5.1

What's Changed

• Remove vertex labels when performing edge union by @Joseph-Edwards in #507
• Remove doc/*.js, doc/*.css, doc/chooser.html from the repo by @wilfwilson in #511
• DigraphAddEdge: do not add an edge label if edge labels are not yet initialised by @wilfwilson in #509
• kernel: fix check in OutNeighbours by @james-d-mitchell in #519
• Fix compatibility with grape by @fingolfin in #530

New Contributors

• @Joseph-Edwards made their first contribution in #507

Full Changelog: v1.5.0...v1.5.1

1.5.0

This is a fairly major release of the Digraphs package, containing some bugfixes and several new features.

In this version, we welcome Finn Buck, Tom Conti-Leslie, Ewan Gilligan, Lea Racine, and Ben Spiers as contributors to the package.

Bugfixes

• The edge labels of Cayley digraphs could sometimes be incorrect (Fixed by Jan De Beule in PR #452)
• Typos in the documentation of IsDirectedTree and an error message for OnDigraphs were fixed (Wilf A. Wilson in PRs #480 and #498)

A database of one-off named graphs and digraphs, and more families of standard examples

We especially wish to highlight the greatly expanded functionality for creating digraphs that are either famous one-off examples, or are part of a family of standard examples.

In particular, Finn Buck, Lea Racine, James D. Mitchell, Marina Anagnostopoulou-Merkouri, and Ben Spiers implemented functions to construct many more families of standard examples (currently documented in Section 3.5), which were added in in PRs
#408, #409, #411, #415, #416, #417, #423, #424, #425, #445, #454, #456, and #490.

Furthermore, Reinis Cirpons, Tom Conti-Leslie, and Murray Whyte added a database of one-off named graphs and digraphs in PR #404.
These digraphs can be constructed by calling Digraph with a string of appropriate name, e.g. Digraph("brinkmann").
The available names can be accessed with the ListNamedDigraphs function.

Other new features

• Tarjan and Lengauer's almost-linear time dominators algorithm was implemented, and is available via Dominators and DominatorTree (James D. Mitchell, Marina Anagnostopoulou-Merkouri, Samantha Harper, and Finn Buck, in PR #336)
• MaximalCommonSubdigraph and MinimalCommonSuperdigraph were introduced (Luke Elliot, PR #361)
• DigraphShortestPathSpanningTree was introduced (Jan De Beule and Wilf A. Wilson, in PR #363)
• Lawler and Byskov's algorithms for chromatic number were implemented (Ewan Gilligan, PR #382)
• Cayley digraphs now have pre-set vertex and edge labels (Jan De Beule and Wilf A. Wilson, in PR #385)
• DigraphCycle was added as a synonym for CycleDigraph (Wilf A. Wilson, PR #441)
• Several new digraph product operations were introduced: StrongProduct, ConormalProduct, HomomorphicProduct, and LexicographicProduct (Finn Buck, PR #460)
• The operation IsDigraphPath was introduced (James D. Mitchell, PR #489)

Other changes

• The ViewString and inherently known properties of trees, forests, cycle digraphs and tournaments were improved (Wilf A. Wilson in PRs #440 and #447)
• Some technical changes to the package were made by James D. Mitchell in PR #488 and by Max Horn in PR #502

1.4.1

This minor release contains several bugfixes and technical changes,
and improvements to the documentation. These include the following:

• OutNeighbours is now a global function rather than an attribute
  (James D. Mitchell, PR #413).
• The configuration options for Digraphs are now described in the manual
  (James D. Mitchell, PR #420).
• The included version of the Edge Addition Planarity Suite has been updated
  from version 3.0.0.5 to 3.0.1.0, and is now documented in the manual
  (James D. Mitchell, PRs #421,
  #422).
• SetDigraphVertexLabels now accepts an immutable list of labels
  (Murray Whyte, PR #427).
• A bug was fixed in DigraphCore that could lead to wrong results
  (Wilf A. Wilson, PR #437).
• The performance of ChromaticNumber was improved in some cases by the
  use of Brooks' theorem
  (Wilf A. Wilson, PR #446).
• A bug, reported by Leonard Soicher, was fixed in DigraphMaximumMatching
  which affected digraphs with custom vertex labels
  (Wilf A. Wilson, PR #462).
• A bug was fixed that affected DigraphEdgeUnion, DigraphJoin,
  DigraphDisjointUnion, DigraphDirectProduct, and DigraphCartesianProduct
  when each was given a single list of digraphs as the argument.
  (Wilf A. Wilson, PR #468).

1.4.0

In this release there are several new features and improvements.

The following improvements and bugs have been made:

• the clique finder was reimplemented in C by Julius Jonusas
• a critical bug in CayleyDigraph was reported and fixed by Jan De Beule
• a minor bug in ReadDigraphs was reported by Wilf A. Wilson and fixed by James D. Mitchell
• the performance of BlissCanonicalLabelling and BlissAutomorphismGroup was improved for multidigraphs by Marina Anagnostopoulou-Merkouri and Sam Harper.
• a bug in GeneratorsOfEndomorphismMonoid that caused GAP to crash when called with a multidigraph was reported by Wilf A. Wilson and fixed by James D. Mitchell
• Wilf A. Wilson made some improvements to the manual.
• the performance of DigraphCopy was improved by Marina Anagnostopoulou-Merkouri and Sam Harper.

The main new features are:

• the attribute DigraphNrLoops was introduced by Marina Anagnostopoulou-Merkouri and Sam Harper.
• the operations
  • DotColoredDigraph
  • DotVertexColoredDigraph
  • DotEdgeColoredDigraph
  • DotSymmetricColoredDigraph
  • DotSymmetricVertexColoredDigraph
  • DotSymmetricEdgeColoredDigraph
    were introduced by Marina Anagnostopoulou-Merkouri and Sam Harper.
• the operation VerticesReachableFrom was introduced by Marina Anagnostopoulou-Merkouri.
• the operation ModularProduct was introduced by Luke Elliott and James D. Mitchell

1.3.1

This is a minor release fixing some issues, some performance improvements, and removing some deprecated code. The changes in this release were made by Max Horn and Wilf A. Wilson.

1.3.0

This is a minor release adding the new functionality DigraphMutabilityFilter,StrongOrientation, Bridges, and IsBridgeless [James D. Mitchell].

1.2.1

This is a minor release where some of the documentation has been fixed and the installation instructions have been improved James D. Mitchell, some changes were made for compatibility with future versions of GAP Max Horn and Wilf A. Wilson.

1.2.0

This is a minor release adding some new features to Digraphs, principally functionality relating to computing matchings by Reinis Ciprons, and an implementation of Dijkstra's algorithm for shortest paths by Markus Pfeiffer and Maria Tsalakou, and methods for producing a concise string representation of a digraph by Murray Whyte.

1.1.2

This is a minor release adding the new configuration flag --without-intrinsics and checking that the compiler is in C99 mode by using AC_PROG_CC_C99 in configure.ac.

1.1.1

This release fixes a bug in HomomorphismDigraphsFinder that was introduced in version 1.1.0. The bug was found and fixed by James D. Mitchell; see PR #290.