GAP (ANUPQ) - Chapter 1: Introduction

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1 Introduction
1.1 Overview
1.2 How to read this manual
1.3 Authors and Acknowledgements

### 1 Introduction

#### 1.1 Overview

The GAP 4 package ANUPQ provides an interface to the ANU `pq` C progam written by Eamonn O'Brien, making the functionality of the C program available to GAP. Henceforth, we shall refer to the ANUPQ package when referring to the GAP interface, and to the ANU `pq` program or just `pq` when referring to that C program.

The `pq` program consists of implementations of the following algorithms:

1. A p-quotient algorithm to compute pc-presentations for p-factor groups of finitely presented groups.

2. A p-group generation algorithm to generate pc presentations of groups of prime power order.

3. A standard presentation algorithm used to compute a canonical pc-presentation of a p-group.

4. An algorithm which can be used to compute the automorphism group of a p-group.

   This part of the `pq` program is not accessible through the ANUPQ package. Instead, users are advised to consider the GAP 4 package AutPGrp by Bettina Eick and Eamonn O'Brien, which implements a better algorithm in GAP for the computation of automorphism groups of p-groups.

The current version of the ANUPQ package requires GAP 4.5, and version 1.5 of the AutPGrp package. All code that made the package compatible with earlier versions of GAP has been removed. If you must use an older GAP version and cannot upgrade, then you may try using an older ANUPQ version. However, you should not use versions of the ANUPQ package older than 2.2, since they are known to have bugs.

#### 1.2 How to read this manual

It is not expected that readers of this manual will read it in a linear fashion from cover to cover; some sections contain material that is far too technical to be absorbed on a first reading.

Firstly, installers of the ANUPQ package will need to read Chapter Installing the ANUPQ Package, if they have not already gleaned these details from the `README` file.

Once the ANUPQ package is installed, users of the ANUPQ package will benefit most by first reading Chapter Mathematical Background and Terminology, which gives a brief description of the background and terminology used (this chapter also cites a number of references for further reading), and the introduction of Chapter Infrastructure (skip the remainder of the chapter on a first reading).

Then the user/reader should pursue Chapter Non-interactive ANUPQ functions in detail, delving into Chapter ANUPQ Options as necessary for the options of the functions that are described. The user will become best acquainted with the ANUPQ package by trying the examples. This chapter describes the non-interactive functions of the ANUPQ package, i.e. "one-shot" functions that invoke the `pq` program in such a way that once GAP has got what it needs, the `pq` is allowed to exit. It is expected that most of the time, users will only need these functions.

Advanced users will want to explore Chapter Interactive ANUPQ functions which describes all the interactive functions of the ANUPQ package; these are functions that extract information via a dialogue with a running `pq` process. Occasionally, a user needs the "next step"; the functions provided in this chapter make use of data from previous steps retained by the `pq` program, thus allowing the user to interact with the `pq` program like one can when one uses the `pq` program as a stand-alone (see `guide.dvi` in the `standalone-doc` directory).

After having read Chapters Non-interactive ANUPQ functions and Interactive ANUPQ functions, cross-references will have taken the reader into Chapter ANUPQ Options; by this stage, the reader need only read the introduction of Chapter ANUPQ Options.

After the reader has developed some facility with the ANUPQ package, she should explore the examples described in Appendix Examples.

If you run into trouble using the ANUPQ functions, some troubleshooting hints are given in Section Hints and Warnings regarding the use of Options. If the troubleshooting hints don't help, Section Authors and Acknowledgements below, gives contact details for the authors of the components of the ANUPQ package.

#### 1.3 Authors and Acknowledgements

The C implementation of the ANU `pq` standalone was developed by Eamonn O'Brien.

An interactive interface using iostreams was developed with the assistance of Werner Nickel by Greg Gamble.

The GAP 4 version of this package was adapted from the GAP 3 version by Werner Nickel.

A new co-maintainer, Max Horn, joined the team in November, 2011.

The authors would like to thank Joachim Neubüser for his careful proof-reading and advice, and for formulating Chapter Mathematical Background and Terminology.

We would also like to thank Bettina Eick who by her testing and provision of examples helped us to eliminate a number of bugs and who provided a number of valuable suggestions for extensions of the package beyond the GAP 3 capabilities.

If you find a bug, the last section of ANUPQ's `README` describes the information we need and where to send us a bug report; please take the time to read this (i.e. help us to help you).

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