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README - Semigroups package for GAP

Copyright (C) 2011-21 James D. Mitchell et al.
Licensing information is available in the LICENSE file.


Getting Semigroups

To get the latest version of the package download the archive file semigroups-x.x.x.tar.gz from the Semigroups webpage, and inside the pkg subdirectory of your GAP installation unpack semigroups-x.x.x.tar.gz, by, for example, doing:

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

This will create a subdirectory semigroups-x.x.x.


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


It is assumed that you have a working copy of GAP with version number 4.10.0 or higher. The most up-to-date version of GAP and instructions on how to install it can be obtained from the main GAP page.

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

  • get the datastructures package version 0.2.5 or higher

  • ensure that the Digraphs package version 1.2.0 or higher is available. Digraphs must be compiled before Semigroups can be loaded.

  • get the genss package version 1.6.5 or higher

  • get the images package version 1.3.0 or

  • get the IO package version 4.5.1 or higher

  • get the orb package version 4.8.2 or higher

Both orb and Semigroups perform better when orb is compiled, so compile orb!

  • download the package archive semigroups-x.x.x.tar.gz from the Semigroups webpage.

  • unzip and untar the file semigroups-x.x.x.tar.gz, for example, using

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

    this should create a directory called semigroups-x.x.x.

  • locate the pkg directory of your GAP directory, which contains the directories lib, doc, and so on. Move the directory semigroups-x.x.x into the pkg directory.

  • from version 3.0.0, it is necessary to compile the Semigroups package. Semigroups uses the libsemigroups C++ library, which requires a compiler

    implementing the C++11 standard.

    You may either build libsemigroups along with Semigroups, or have it installed at a custom or standard location, as explained in its documentation. To compile in the former case, inside the pkg/semigroups-x.x.x directory, type

    • ./configure
    • make

    For the latter case, you need a working pkg-config tool; assuming libsemigroups was installed at location /foo/bar, type

    • PKG_CONFIG_PATH=/foo/bar/lib/pkgconfig ./configure --with-external-libsemigroups
    • make

    If pkg-config has /foo/bar among its default locations, then PKG_CONFIG_PATH=/foo/bar/lib/pkgconfig part above may be omitted).

    If you are using GCC to compile Semigroups, then version 5.0 or higher is required. Trying to compile Semigroups with an earlier version of GCC will result in an error at compile time. Semigroups supports GCC version 5.0 or higher, and clang version 5.0 or higher.

    Further information about this step can be found in manual section entitled “Compiling the kernel module”.

  • start GAP in the usual way.

  • type LoadPackage("semigroups");