
<!-- %W  atlasrep.xml    GAP 4 package AtlasRep             Thomas Breuer -->
<!-- %Y  Copyright 2001, Lehrstuhl D für Mathematik, RWTH Aachen, Germany -->


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<Chapter Label="chap:atlasrep">
<Heading>Customizations of the &AtlasRep; Package</Heading>


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<Section Label="sect:Installing the AtlasRep Package">
<Heading>Installing the &AtlasRep; Package</Heading>

To install the package, unpack the archive file in a
directory in the <F>pkg</F> directory of your local copy of &GAP;&nbsp;4.
This might be the <F>pkg</F> directory of the &GAP;&nbsp;4 root directory,
see&nbsp;<Ref Sect="Installing a GAP Package" BookName="ref"/>
for details.
It is however also possible to keep an additional <F>pkg</F> directory
somewhere else,
see Section&nbsp;<Ref Sect="GAP Root Directories" BookName="ref"/>.
The latter possibility <E>must</E> be chosen if you do not have write access
to the &GAP; root directory.

<P/>

If it is likely that you will work offline, it makes sense to install the
<Q>starter archive</Q> that can be downloaded from the package's homepage.

<P/>

The package consists entirely of &GAP; code,
no external binaries need to be compiled for the package itself.

<P/>

After unpacking the package archive,
the write permissions for those directories should be checked
into which users will download files.
Every user can customize these paths via a user preference,
see Section <Ref Subsect="subsect:AtlasRepDataDirectory"/>,
the defaults are the subdirectories 
<F>data*</F> of the package directory.
The recommended permissions under UNIX for the default directories
are set as follows.

<P/>

<Log><![CDATA[
you@unix> chmod 1777 atlasrep/data*
you@unix> ls -ld atlasrep/data*
drwxrwxrwt   3 you      you          1024 Apr 12 12:34 dataext
drwxrwxrwt   3 you      you          1024 Apr 12 12:34 datagens
drwxrwxrwt   3 you      you          1024 Apr 12 12:34 datapkg
drwxrwxrwt   3 you      you          1024 Apr 12 12:34 dataword
]]></Log>

<P/>

<#Include Label="[1]{testinst.g}">

<P/>

PDF, HTML, and text versions of the package manual are available
in the <F>doc</F> directory of the package.

</Section>


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<Section Label="sect:atlasrep user preferences">
<Heading>User Preferences of the &AtlasRep; Package</Heading>

This section describes global parameters for which it might make sense
to change their defaults, using &GAP;'s user preferences
(see <Ref Subsect="Configuring User preferences" BookName="ref"/>).

<P/>

<List>
<Item>
  Is access to remote data allowed
  (see Section <Ref Subsect="subsect:AtlasRepAccessRemoteFiles"/>)?
  If yes then also the following parameters are of interest.
  <P/>
  <List>
    <Item>
      From where can the data be fetched
      (see Section <Ref Subsect="subsect:AtlasRepTOCData"/>)?
    </Item>
    <Item>
      Where are local copies of these data stored
      (see Section <Ref Subsect="subsect:AtlasRepDataDirectory"/>)?
    </Item>
    <Item>
      Shall files be compressed after they have been downloaded
      (see Section <Ref Subsect="subsect:CompressDownloadedMeatAxeFiles"/>)?
    </Item>
  </List>
</Item>
<Item>
  The following parameters influence reading and writing of local files.
  <P/>
  <List>
    <Item>
      What shall actually happen when data are requested by the interface
      functions (see Section <Ref Subsect="subsect:FileAccessFunctions"/>)?
    </Item>
    <Item>
      If the value of the user preference <C>FileAccessFunctions</C>
      contains <C>"direct access to a local server"</C>,
      what is its path
      (see Section <Ref Subsect="subsect:AtlasRepLocalServerPath"/>)?
    </Item>
    <Item>
      Shall <Ref Func="ScanMeatAxeFile"/> focus on small runtime or on small
      space when reading &MeatAxe; text files
      (see Section <Ref Subsect="subsect:HowToReadMeatAxeTextFiles"/>)?
    </Item>
    <Item>
      Which kind of headers shall <Ref Func="MeatAxeString"/> create
      (see Section <Ref Subsect="subsect:WriteHeaderFormatOfMeatAxeFiles"/>)?
    </Item>
    <Item>
      Shall <Ref Func="MeatAxeString"/> interpret permutation matrices more as
      permutations (mode 2) or as matrices (mode 1 or 6)
      (see Section <Ref Subsect="subsect:WriteMeatAxeFilesOfMode2"/>)?
    </Item>
    <Item>
      Shall the default for <Ref Func="CMtxBinaryFFMatOrPerm"/> be to write
      binary files of zero-based or one-based permutations
      (see Section <Ref Subsect="subsect:BaseOfMeatAxePermutation"/>)?
    </Item>
  </List>
</Item>
<Item>
  Which function is used by <Ref Func="DisplayAtlasInfo"/> for printing to
  the screen
  (see Section <Ref Subsect="subsect:DisplayFunction"/>)?
</Item>
<Item>
  How does <Ref Func="DisplayAtlasInfo"/> mark data that do not belong
  to the core database
  (see Section <Ref Subsect="subsect:AtlasRepMarkNonCoreData"/>)?
</Item>
<Item>
  Shall debug messages be printed when local data files are read
  (see Section <Ref Subsect="subsect:DebugFileLoading"/>)?
</Item>
</List>

<#Include Label="AtlasRepAccessRemoteFiles">
<#Include Label="AtlasRepDataDirectory">
<#Include Label="AtlasRepTOCData">
<#Include Label="CompressDownloadedMeatAxeFiles">
<#Include Label="FileAccessFunctions">
<#Include Label="AtlasRepLocalServerPath">
<#Include Label="HowToReadMeatAxeTextFiles">
<#Include Label="WriteHeaderFormatOfMeatAxeFiles">
<#Include Label="WriteMeatAxeFilesOfMode2">
<#Include Label="BaseOfMeatAxePermutation">
<#Include Label="DisplayFunction">
<#Include Label="AtlasRepMarkNonCoreData">
<#Include Label="DebugFileLoading">
<#Include Label="AtlasRepJsonFilesAddresses">

</Section>


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<Section Label="sect:Web Contents for the AtlasRep Package">
<Heading>Web Contents for the &AtlasRep; Package</Heading>

The <URL><Link>&ATLASREPHOME;</Link><LinkText>home page of the &AtlasRep; package</LinkText></URL>
provides

<P/>

<List>
<Item>
  package archives,
</Item>
<Item>
  introductory package information,
</Item>
<Item>
  the current <E>table of contents</E> of core data in the file
  <URL><LinkText><F>atlasprm.json</F></LinkText><Link>&ATLASREPHOME;/atlasprm.json</Link></URL>
  of the package,
  cf.&nbsp;<Ref Func="StringOfAtlasTableOfContents"/>,
</Item>
<Item>
  the <URL><LinkText>list of changes of remote core data files</LinkText><Link>&ATLASREPHOME;/htm/data/changes.htm</Link></URL>,
</Item>
<Item>
  a <URL><LinkText>starter archive</LinkText><Link>&ATLASREPHOME;/atlasrepdata.tar.gz</Link></URL>
  containing many small representations and programs,
  and
</Item>
<Item>
  an <URL><LinkText>overview of the core data</LinkText><Link>&ATLASREPHOME;/htm/data</Link></URL>
  in a similar format as the information shown by the function
  <Ref Func="DisplayAtlasInfo"/> of the package;
  more details can be found on the
  <URL><LinkText>home page of the &ATLAS; of Group Representations</LinkText><Link>&ATLASSERVER;</Link></URL>.
</Item>
</List>

</Section>


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<Section Label="sect:Extending the Atlas Database">
<Heading>Extending the &ATLAS; Database</Heading>

Users who have computed new representations that might be interesting for
inclusion into the &ATLAS; of Group representations can send the data in
question to&nbsp;&WILSONMAIL;.

<P/>

It is also possible to make additional representations and programs
accessible for the &GAP; interface,
and to use these <Q>private</Q> data in the same way as the core data.
See Chapter&nbsp;<Ref Chap="chap:Private Extensions"/> for details.

</Section>


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</Chapter>

