# Digraphs

Graphs, digraphs, and multidigraphs in GAP

Version 1.0.3
Released 2019-11-29

This project is maintained by James Mitchell, Wilf Wilson

## Getting Digraphs

To get the latest version of the package, download the archive file digraphs-x.x.x.tar.gz from the Digraphs webpage. Then, inside the pkg subdirectory of your GAP installation, unpack the archive digraphs-x.x.x.tar.gz, using

gunzip digraphs-x.x.x.tar.gz; tar xvf digraphs-x.x.x.tar


for example. This will create a subdirectory digraphs-x.x.x.

## Issues

For questions, remarks, suggestions, and issues please use the issue tracker.

## Installation

It is assumed that you have a working copy of GAP with version number 4.9.0 or higher. The most up-to-date version of GAP, and instructions on how to install it, can be obtained from the main GAP webpage.

The following is a summary of the steps that should lead to a successful installation of Digraphs:

• get the IO package version 4.5.1 or higher.
• get the orb package version 4.8.2 or higher.
• this step is optional: certain methods in Digraphs require the Grape package to be available; a full list of these functions can be found in the first chapter of the manual. To use these functions make sure that the Grape package version 4.8.1 or higher is available.
• download the package archive digraphs-x.x.x.tar.gz from the Digraphs webpage.
• unzip and untar the file digraphs-x.x.x.tar.gz using, for example,
  gunzip digraphs-x.x.x.tar.gz; tar xvf digraphs-x.x.x.tar


which should create a directory called digraphs-x.x.x.

• locate the pkg directory of your GAP directory, which contains the directories lib, doc and so on. Move the directory digraphs-x.x.x into the pkg directory (if it is not there already).
• compile the kernel module; more details are given below.
• start GAP in the usual way.
• type LoadPackage("digraphs");

## Compiling the kernel module

The Digraphs package has a GAP kernel component written in C, which has to be compiled in order for the package to work. This component contains certain low-level functions that the package requires.

It is not possible to use the Digraphs package without compiling it.

To compile the kernel component inside the digraphs-x.x.x directory, type

./configure
make


If you installed the package in a pkg directory other than the standard pkg directory in your GAP installation, then you have to do two things. Firstly, during compilation you have to use the option --with-gaproot=PATH of the configure script where PATH is a path to the main GAP root directory (if not given, the default ../.. is assumed).

If you installed GAP on several architectures, then you must execute the configure/make step for each of the architectures. You can either do this immediately after configuring and compiling GAP itself on this architecture, or alternatively set the environment variable CONFIGNAME to the name of the configuration you used when compiling GAPbefore running ./configure. Note however that your compiler choice and flags (environment variables CC and CFLAGS) need to be chosen to match the setup of the original GAP compilation. For example, you have to specify 32-bit or 64-bit mode correctly!

Digraphs vendors bliss and planarity libraries in the extern directory. If you wish to use your system copy of bliss or planarity, please use the configure options --with-external-bliss or --with-external-planarity, as appropriate.

If you wish to install a development version of the Digraphs package, then you must first run the command ./autogen.sh before compilation. However, development versions of the package may be unstable, and we recommend using the most recently released version of the package when possible.

Enjoy!