Computations with iterated monodromy groups

Version 0.2.3

This project is maintained by Laurent Bartholdi

                             The IMG package

This is the README file for the GAP package "IMG".

This package implements Iterated Monodromy groups.

This release (0.0) is the first containing the basic functionality,
though some rough edges will still need to be smoothed. In particular,
the TODO file describes plans for future development, including
computations of presentations for self-similar groups, interval arithmetic
for complex dynamics, etc.

The package is distributed in source form, and does not require anything
else than a running GAP 4.5 or later. For updates, check

To use the package, start GAP and type


The "IMG" package banner should appear on the screen.

For details on how to use the IMG package, please consult the documentation.
Though this is usually not necessary, it may be recompiled, after the command
`LoadPackage("IMG")', by invoking


at the GAP prompt. The documentation will then be available in the `doc'
subdirectory (view the file `manual.pdf' via a PDF viewer).

An external module (DLL) provides floating-point functions used for complex
dynamics calculations. To compile it, first make sure that your system has C
and JAVA compilers. IMG needs some external libraries, but they are included
in the subdirectory `extern'. If your system has them, their location can
be specified using the arguments `--with-levmar' and `--with-libdogleg' to
the `./configure' script. The options `--with-gaproot', `--with-gaparch' and
`CONFIGNAME' tell IMG where to look for the GAP installation; by default,
IMG searches for it in ../.. and /usr/local/src/gap. The library `cholmod'
is also required (often part of suitesparse), but is not provided.

In all cases, then run

'./configure && make' in IMG's root directory.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or any
later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program, in the file COPYING.  If not, see

  Laurent Bartholdi, Göttingen, 19 November 2012