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.

1.1.0

This is a minor release that includes some new features and some performance improvements.

The following issues were resolved, pull requests merged, or new features added:

• Issue #40: If bliss is used to compute the automorphism group of a digraph, then the size of the automorphism group is returned from bliss to GAP, and the group object in GAP immediately knows its size. In particular, it is not necessary to recalculate this size. This was reported and fixed in PR #278 by Chris Jefferson.

• Issue #279: In the function HomomorphismDigraphsFinder, it is now possible to specify a subgroup of the automorphism group of the range digraph. This way, the automorphism group of the range digraph is not computed by HomomorphismDigraphsFinder. This can result in a performance improvement in some cases. This was reported and fixed in PR #285 by Finn Smith.

• Issue #284: The function HomomorphismDigraphsFinder sometimes did not return any homomorphisms when the source digraph had exactly one vertex. This was caused by the data structures used by HomomorphismDigraphsFinder not being correctly initialised in this case. This issue was reported by Finn Smith and fixed by James D. Mitchell in PR #286.

• In PR #283, Finn Smith added the new operation DigraphsRespectsColouring, which can be used to check whether a transformation or permutation between digraphs respects given colourings. New versions of IsDigraphHomomorphism, and friends, were added that accept colourings as arguments and which use DigraphsRespectsColouring.

• The version of bliss included in Digraphs was updated to allow all of its data structures to be modified in-place rather than allocated and deallocated repeatedly. The function HomomorphismDigraphsFinder was modified to make use of this new functionality in bliss, and subsequently the performance of HomomorphismDigraphsFinder has been improved (particularly in cases where many homomorphisms between distinct small digraphs are found). This was done by James D. Mitchell in PR #282.

• Some further minor performance improvements were made, and a compiler warning was fixed.

1.0.3

This is a minor release that fixes some bugs related to mutability in DigraphDisjointUnion and ViewString.

These problems were reported and fixed by Wilf A. Wilson in Issue #276 and PR #277, respectively.