GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
1<!-- %W atlasrep.xml GAP 4 package AtlasRep Thomas Breuer -->2<!-- %Y Copyright 2001, Lehrstuhl D f�r Mathematik, RWTH Aachen, Germany -->345<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->6<Chapter Label="chap:atlasrep">7<Heading>Customizations of the <Package>AtlasRep</Package> Package</Heading>8910<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->11<Section Label="sect:Installing the AtlasRep Package">12<Heading>Installing the <Package>AtlasRep</Package> Package</Heading>1314To install the package, unpack the archive file in a15directory in the <F>pkg</F> directory of your local copy of &GAP; 4.16This might be the <F>pkg</F> directory of the &GAP; 4 root directory,17see <Ref Sect="Installing a GAP Package" BookName="ref"/>18for details.19It is however also possible to keep an additional <F>pkg</F> directory20in your private directories,21see Section <Ref Sect="GAP Root Directories" BookName="ref"/>.22The latter possibility <E>must</E> be chosen if you do not have write access23to the &GAP; root directory.2425<P/>2627Data files that are available from an earlier version28of the package are in principle kept;29see <Ref30Func="AtlasOfGroupRepresentationsTestTableOfContentsRemoteUpdates"/>31for necessary updates.3233<P/>3435If it is likely that one will work offline, it makes sense to install the36<Q>starter archive</Q> that can be downloaded from the package's homepage.3738<P/>3940The package consists entirely of &GAP; code,41no external binaries need to be compiled for the package itself.42However, if the &GAP; package <Package>IO</Package> <Cite Key="IO"/>43<Index>IO package</Index>44is used to access remote data files45(see Section <Ref Sect="subsect:Accessing data files with wget or IO"/>)46then its external binary must be available.4748<P/>4950After unpacking the package archive,51the write permissions for those directories should be checked52into which users will download files.53Every user can customize these paths via a user preference,54see Section <Ref Subsect="subsect:AtlasRepDataDirectory"/>,55the defaults are the subdirectories56<F>datagens</F> and <F>dataword</F> of the package directory.57The recommended permissions under UNIX for the default directories58are set as follows.5960<P/>6162<Log><![CDATA[63you@unix> chmod 1777 atlasrep/data*64you@unix> ls -ld atlasrep/data*65drwxrwxrwt 3 you you 1024 Oct 31 12:34 datagens66drwxrwxrwt 3 you you 1024 Oct 31 12:34 dataword67]]></Log>6869<P/>7071<#Include Label="[1]{testinst.g}">7273<P/>7475PDF, HTML, and text versions of the package manual are available76in the <F>doc</F> directory of the package.7778</Section>798081<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->82<Section Label="sect:Maintaining the Local Data of the AtlasRep Package">83<Heading>Maintaining the Local Data of the <Package>AtlasRep</Package>84Package</Heading>8586<!-- The section title is referenced in index.html. -->87<Alt Only="HTML"><![CDATA[<a id="sect:maintain"/>]]></Alt>8889The current <E>table of contents</E> of the database is contained in90the file <F>gap/atlasprm.g</F> of the <Package>AtlasRep</Package> package.91This file is read by default when the package is loaded.92It may happen that new data files have been added to the servers since the93last release of the <Package>AtlasRep</Package> package,94thus it is useful to update the table of contents of the package95from time to time.9697<P/>9899For that, one can fetch the most recent version of the file100<F>gap/atlasprm.g</F> from the home page of the package101(see Section <Ref Sect="sect:Web Services for the AtlasRep Package"/>),102either by calling <Ref Func="ReloadAtlasTableOfContents"/>103in a &GAP; session104or <Q>by hand</Q>.105In the latter case, the new file can then be read into the &GAP; session via106<Ref Func="ReplaceAtlasTableOfContents"/>.107<#Include Label="ATLASREP_TOCFILE">108109<P/>110111Users who have write access to the directory where the112<Package>AtlasRep</Package> package is113installed can alternatively use the <F>maketoc</F> script in the <F>etc</F>114directory of the package for regularly updating the file115<F>gap/atlasprm.g</F>.116Users without this write access can store the new file in a different place,117and read it with <Ref Func="ReplaceAtlasTableOfContents"/>.118119<P/>120121<#Include Label="ReloadAtlasTableOfContents">122<#Include Label="StoreAtlasTableOfContents">123<#Include Label="ReplaceAtlasTableOfContents">124<#Include Label="AGRTestTableOfContentsRemoteUpdates">125126</Section>127128129<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->130<Section Label="sect:User Parameters for the AtlasRep Package">131<Heading>User Parameters for the <Package>AtlasRep</Package> Package</Heading>132133This section lists global parameters for which it might make sense134to change their defaults by assignments to global variables135(see <Ref Func="AtlasOfGroupRepresentationsUserParameters"/>136for an overview of these parameters)137or using &GAP;'s user preferences138(see <Ref Subsect="Configuring User preferences" BookName="ref"/>).139140141<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->142<Subsection Label="subsect:Local or remote access">143<Heading>Local or Remote Access</Heading>144145<Index>local access</Index>146<Index>remote access</Index>147<Index>servers</Index>148There are two possibilities to use the <Package>AtlasRep</Package> package.149150<P/>151152<List>153<Mark><E>Local access only (offline)</E></Mark>154<Item>155You can restrict the access to the data that are actually stored in156the local installation of &GAP;.157</Item>158<Mark><E>Remote access (online)</E></Mark>159<Item>160If your computer is connected to a network that provides access to161the &ATLAS; data (for example the internet) then the functions of the162package may fetch the requested data automatically from remote servers163when they are required for the first time;164these data are then by default stored in the local copy,165so later access to them needs no network transfer.166</Item>167</List>168169<P/>170171The latter possibility is presently not used by other &GAP; packages,172so it may be regarded as an important feature of the173<Package>AtlasRep</Package> package.174Anyhow it requires a few words of explanation.175176<P/>177178The possibility of online access reflects in particular the fact179that the &ATLAS; of Group Representations is designed180as an <E>open database</E>, it is expected to grow.181As soon as the developers of the &ATLAS; of Group Representations add182new information to the servers,183these data become available in &GAP; when remote access is enabled,184after one has updated the corresponding table of contents185(see Section <Ref Sect="sect:Maintaining the Local Data of the AtlasRep Package"/>).186187<P/>188189Remote access is enabled if and only if the value of the <C>remote</C>190component of the global variable191<Ref Var="AtlasOfGroupRepresentationsInfo"/> is <K>true</K>.192If one wants to work offline, i.e., if one does <E>not</E> want &GAP;193to attempt accessing remote data194then this value must be set to <K>false</K>.195196<P/>197198Conversely, if the default value of the <C>remote</C> component199in your &GAP; installation is <K>false</K>200then changing this value to <K>true</K> may be not successful.201First, it might be the case that no server is reachable.202And second, if one can in principle <E>download</E> files from a server then203it might be impossible to actually <E>store</E> these files204in the data directories of the installed package;205in this case, it is advisable to install the whole package206or just its data directories in a private directory,207see <Ref Sect="GAP Root Directories" BookName="ref"/> for details.208209</Subsection>210211212<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->213<Subsection Label="subsect:Adding and Removing Servers">214<Heading>Adding and Removing Servers</Heading>215216When access to remote data is enabled217(see Section <Ref Sect="subsect:Local or remote access"/>)218then the available servers are given by the <C>servers</C> component219of the global variable <Ref Var="AtlasOfGroupRepresentationsInfo"/>.220221<P/>222223<E>Removing</E> entries from this list means to disable access to the224corresponding servers,225<E>adding</E> entries makes the corresponding servers available.226Of course the latter makes sense only if the new servers really exist,227for example in a local network.228229<P/>230231Currently there is just one remote server.232As soon as other servers become available, or a server name is changed233which makes it necessary to adjust the <C>servers</C> component,234this will be announced in the &GAP; Forum, cf.235<Ref Sect="Further Information about GAP" BookName="tut"/>.236The same holds when upgrades of the package become available.237238</Subsection>239240241<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->242<Subsection Label="subsect:Accessing data files with wget or IO">243<Heading>Accessing Data Files with the &GAP; Package <Package>IO</Package>244or with <F>wget</F></Heading>245246<#Include Label="IO_or_wget">247248</Subsection>249250251<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->252<Subsection Label="subsect:Compressed or uncompressed data files">253<Heading>Compressed or Uncompressed Data Files</Heading>254255When used with UNIX, &GAP; can read <F>gzip</F>ped files,256see <Ref Sect="Saving and Loading a Workspace" BookName="ref"/>.257If the component <C>compress</C>258<Index Key ="compress"><C>compress</C></Index>259of <Ref Var="AtlasOfGroupRepresentationsInfo"/> has the value <K>true</K>260then each &MeatAxe; format file that is fetched from a remote261server is afterwards compressed with <F>gzip</F>.262<Index Key ="gzip"><F>gzip</F></Index>263This saves a lot of space if many &MeatAxe; format files are accessed.264(Note that data files in other formats are very small.)265For example, at the time of the release of version 1.5.1 there were about266<M>8\,400</M> data files in &MeatAxe; format,267which needed about <M>1\,400</M> MB in uncompressed text format268and about <M>275</M> MB in compressed text format.269The default value for the component <C>compress</C> is <K>false</K>.270271</Subsection>272273274<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->275<Subsection Label="subsect:Customizing DisplayAtlasInfo">276<Heading>Customizing <C>DisplayAtlasInfo</C></Heading>277278The way how <Ref Func="DisplayAtlasInfo"/> shows the requested overview279is controlled by the component <C>displayFunction</C>280of <Ref Var="AtlasOfGroupRepresentationsInfo"/>.281The default value is <Ref Func="Print" BookName="ref"/>,282other useful values are <Ref Func="PrintFormattedString" BookName="gapdoc"/>283and <C>AGR.Pager</C>;284the latter calls <Ref Func="Pager" BookName="ref"/> with the <C>formatted</C>285option, which is necessary for switching off &GAP;'s automatic line breaking.286287</Subsection>288289290<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->291<Subsection Label="subsect:Customizing the Access to Data files">292<Heading>Customizing the Access to Data Files</Heading>293294By default, local data files are stored in the subdirectories <F>datagens</F>295and <F>dataword</F> of the directory given by the user preference296<C>AtlasRepDataDirectory</C>297(see Section <Ref Subsect="subsect:AtlasRepDataDirectory"/>),298and the files are exactly the text files provided on the servers.299However, a more flexible approach may be useful.300301<P/>302303First, one may want to use <E>different file formats</E>,304for example the &MeatAxe; binary files that are provided by the servers305parallel to the &MeatAxe; text files.306Second, one may want to use <E>a different directory structure</E>,307for example the same structure as used on the servers308–this makes sense for example if a local mirror of a server309is available, because then one can read the server files directly,310without transferring/copying them to another directory.311312<P/>313314As a consequence, one would like to customize the meaning of the following315three access steps.316317<P/>318319<List>320<Mark>Are the required files locally available?</Mark>321<Item>322The required files may have a different name or a different path,323and the data can be available in one file or can be distributed to several324files.325</Item>326<Mark>How can a file be made locally available?</Mark>327<Item>328A different server file may be fetched329or some postprocessing may be required.330</Item>331<Mark>How is the data of a file accessed by &GAP;?</Mark>332<Item>333A different function may be needed to read the file.334</Item>335</List>336337<P/>338339Details how to achieve these customizations can be found in Section340<Ref Sect="sect:How to Customize the Access to Data files"/>.341342</Subsection>343344345<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->346<Subsection Label="subsect:Reading large matrices over finite fields">347<Heading>Reading Large Matrices over Finite Fields</Heading>348349Matrices over finite fields in &GAP; can be represented in a compressed350format that needs less space than the corresponding text file.351Such a &MeatAxe; format text file can be read by352<Ref Func="ScanMeatAxeFile"/> either line by line (which is the default)353or as a whole; the latter is faster but needs more space than the former.354For example, a <M>4\,370</M> by <M>4\,370</M> matrix over the field355with two elements356(as occurs for an irreducible representation of the Baby Monster) requires357less than <M>3</M> MB space in &GAP; but the corresponding &MeatAxe; format358text file is more than <M>19</M> MB large,359which means that when one reads the file with the fast variant,360&GAP; will temporarily grow by more than this value.361One can change the mode by setting the global variable362<Ref Var="CMeatAxe.FastRead"/> to <K>true</K> or <K>false</K>, respectively.363364<P/>365366Note that this parameter is meaningful only when367<Ref Func="ScanMeatAxeFile"/> is used.368It has no effect for example if &MeatAxe; binary files are read,369cf. <Ref Func="FFMatOrPermCMtxBinary"/>.370371</Subsection>372373<#Include Label="AtlasOfGroupRepresentationsShowUserParameters">374375<#Include Label="AtlasRepDataDirectory">376<#Include Label="WriteMeatAxeFilesOfMode2">377<#Include Label="BaseOfMeatAxePermutation">378379</Section>380381382<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->383<Section Label="sect:Web Services for the AtlasRep Package">384<Heading>Web Services for the <Package>AtlasRep</Package> Package</Heading>385386The home page of the <Package>AtlasRep</Package> package is387388<P/>389<URL>&ATLASREPHOME;</URL>.390<P/>391392Besides package archives and introductory package information, it provides393394<P/>395396<List>397<Item>398the current file with the <E>table of contents</E>399(the file <F>gap/atlasprm.g</F> of the package, see400<URL>&ATLASREPHOME;/atlasprm.g</URL>),401cf. <Ref Func="ReloadAtlasTableOfContents"/>,402</Item>403<Item>404a <E>starter archive</E>405containing many small representations and programs406(see <URL>&ATLASREPHOME;/atlasrepdata.tar.gz</URL>),407</Item>408<Item>409the list of <E>changes of server files</E> in HTML format410(see <URL>&ATLASREPHOME;/htm/data/changes.htm</URL>),411cf. <Ref Func="AtlasOfGroupRepresentationsTestTableOfContentsRemoteUpdates"/>,412and413</Item>414<Item>415an <E>overview of the data</E> available via the &GAP; interface to the416&ATLAS; of Group Representations, in HTML format (see417<URL>&ATLASREPHOME;/htm/data/overview.htm</URL>);418this is similar to the information shown by <Ref Func="DisplayAtlasInfo"/>,419further information can be found on the home page of the &ATLAS;,420see &ATLASSERVER;.421</Item>422</List>423424</Section>425426427<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->428<Section Label="sect:Extending the Atlas Database">429<Heading>Extending the &ATLAS; Database</Heading>430431Users who have computed new representations that might be interesting for432inclusion into the &ATLAS; of Group representations can send the data in433question to &WILSONMAIL;.434435<P/>436437It is also possible to store <Q>private</Q> representations and programs438in local directories,439and to use them in the same way as the <Q>official</Q> data.440See Chapter <Ref Chap="chap:Private Extensions"/> for details.441442</Section>443444445<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->446447</Chapter>448449450451