  
  [1X4 [33X[0;0YCustomizations of the [5XAtlasRep[105X[101X[1X Package[133X[101X
  
  
  [1X4.1 [33X[0;0YInstalling the [5XAtlasRep[105X[101X[1X Package[133X[101X
  
  [33X[0;0YTo  install  the  package, unpack the archive file in a directory in the [11Xpkg[111X
  directory  of  your  local copy of [5XGAP[105X 4. This might be the [11Xpkg[111X directory of
  the  [5XGAP[105X 4  root  directory,  see [14X'Reference:  Installing a GAP Package'[114X for
  details.  It is however also possible to keep an additional [11Xpkg[111X directory in
  your private directories, see Section [14X'Reference: GAP Root Directories'[114X. The
  latter possibility [13Xmust[113X be chosen if you do not have write access to the [5XGAP[105X
  root directory.[133X
  
  [33X[0;0YData  files that are available from an earlier version of the package are in
  principle                                                              kept;
  see [2XAtlasOfGroupRepresentationsTestTableOfContentsRemoteUpdates[102X  ([14X4.2-4[114X) for
  necessary updates.[133X
  
  [33X[0;0YIf  it  is  likely that one will work offline, it makes sense to install the
  [21Xstarter archive[121X that can be downloaded from the package's homepage.[133X
  
  [33X[0;0YThe  package  consists entirely of [5XGAP[105X code, no external binaries need to be
  compiled  for  the package itself. However, if the [5XGAP[105X package [5XIO[105X [Neu14] is
  used  to  access  remote  data  files  (see Section [14X4.3-3[114X) then its external
  binary must be available.[133X
  
  [33X[0;0YAfter  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 [14X4.3-9[114X, the
  defaults  are  the  subdirectories  [11Xdatagens[111X  and  [11Xdataword[111X  of  the package
  directory.   The   recommended   permissions  under  UNIX  for  the  default
  directories are set as follows.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[28Xyou@unix> chmod 1777 atlasrep/data*[128X[104X
    [4X[28Xyou@unix> ls -ld atlasrep/data*[128X[104X
    [4X[28Xdrwxrwxrwt   3 you      you          1024 Oct 31 12:34 datagens[128X[104X
    [4X[28Xdrwxrwxrwt   3 you      you          1024 Oct 31 12:34 dataword[128X[104X
  [4X[32X[104X
  
  [33X[0;0YFor checking the installation of the package, you should start [5XGAP[105X and call[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XReadPackage( "atlasrep", "tst/testinst.g" );[127X[104X
  [4X[32X[104X
  
  [33X[0;0YIf  the  installation  is  o.k. then the [5XGAP[105X prompt appears without anything
  else  being  printed;  otherwise  the  output  lines tell you what should be
  changed.[133X
  
  [33X[0;0YMore  test  files  are  available  in  the [11Xtst[111X directory of the package, see
  Section  [14X7.8[114X for details.[133X
  
  [33X[0;0YPDF,  HTML, and text versions of the package manual are available in the [11Xdoc[111X
  directory of the package.[133X
  
  
  [1X4.2 [33X[0;0YMaintaining the Local Data of the [5XAtlasRep[105X[101X[1X Package[133X[101X
  
  [33X[0;0YThe  current  [13Xtable  of  contents[113X  of  the database is contained in the file
  [11Xgap/atlasprm.g[111X  of  the  [5XAtlasRep[105X package. This file is read by default when
  the  package is loaded. It may happen that new data files have been added to
  the  servers  since  the  last  release  of the [5XAtlasRep[105X package, thus it is
  useful to update the table of contents of the package from time to time.[133X
  
  [33X[0;0YFor  that,  one can fetch the most recent version of the file [11Xgap/atlasprm.g[111X
  from   the   home   page   of  the  package  (see  Section [14X4.4[114X),  either  by
  calling [2XReloadAtlasTableOfContents[102X  ([14X4.2-1[114X)  in a [5XGAP[105X session or [21Xby hand[121X. In
  the  latter  case,  the  new  file can then be read into the [5XGAP[105X session via
  [2XReplaceAtlasTableOfContents[102X  ([14X4.2-3[114X).  Alternatively,  one can add a line to
  the  user's [11Xgaprc[111X file (see [14X'Reference: The gap.ini and gaprc files'[114X), which
  assigns the filename of the current [11Xgap/atlasprm.g[111X file (as an absolute path
  or   relative  to  the  user's  home  directory,  cf. [2XDirectory[102X  ([14XReference:
  Directory[114X)) to the global variable [10XATLASREP_TOCFILE[110X; in this case, this file
  is read instead of the one from the package distribution when the package is
  loaded.[133X
  
  [33X[0;0YUsers  who  have write access to the directory where the [5XAtlasRep[105X package is
  installed  can  alternatively use the [11Xmaketoc[111X script in the [11Xetc[111X directory of
  the  package  for  regularly updating the file [11Xgap/atlasprm.g[111X. Users without
  this  write  access can store the new file in a different place, and read it
  with [2XReplaceAtlasTableOfContents[102X ([14X4.2-3[114X).[133X
  
  [1X4.2-1 ReloadAtlasTableOfContents[101X
  
  [29X[2XReloadAtlasTableOfContents[102X( [3Xdirname[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Y[9Xfail[109X  if  the  required  table  of contents could not be reloaded,
            otherwise [9Xtrue[109X.[133X
  
  [33X[0;0YLet [3Xdirname[103X be a string, which must be one of [10X"remote"[110X, [10X"local"[110X, or the name
  of a private data directory (see Chapter [14X5[114X).[133X
  
  [33X[0;0YIn  the  case of [10X"remote"[110X, the file [11Xatlasprm.g[111X is fetched from the package's
  home page, and then read into [5XGAP[105X. In the case of [10X"local"[110X, the subset of the
  data  listed  in  the  [10X"remote"[110X  table  of  contents  is considered that are
  actually  available  in the local data directories. In the case of a private
  directory,  its contents is inspected, and the table of contents for [3Xdirname[103X
  is  replaced  by the one obtained from inspecting the actual contents of the
  data directories (see Section [14X7.7[114X).[133X
  
  [1X4.2-2 StoreAtlasTableOfContents[101X
  
  [29X[2XStoreAtlasTableOfContents[102X( [3Xfilename[103X ) [32X function
  
  [33X[0;0YLet  [3Xfilename[103X be a string. This function prints the loaded table of contents
  of the servers to the file with name [3Xfilename[103X.[133X
  
  [1X4.2-3 ReplaceAtlasTableOfContents[101X
  
  [29X[2XReplaceAtlasTableOfContents[102X( [3Xfilename[103X ) [32X function
  
  [33X[0;0YLet   [3Xfilename[103X   be   the  name  of  a  file  that  has  been  created  with
  [2XStoreAtlasTableOfContents[102X ([14X4.2-2[114X).[133X
  
  [33X[0;0Y[2XReplaceAtlasTableOfContents[102X  first  removes  the  information  that  [5XGAP[105X has
  stored  about  the table of contents of the servers, and then reads the file
  with  name  [3Xfilename[103X,  thus replacing the previous information by the stored
  one.[133X
  
  [1X4.2-4 AtlasOfGroupRepresentationsTestTableOfContentsRemoteUpdates[101X
  
  [29X[2XAtlasOfGroupRepresentationsTestTableOfContentsRemoteUpdates[102X(  ) [32X function
  [6XReturns:[106X  [33X[0;10Ythe  list of names of all locally available data files that should
            be removed.[133X
  
  [33X[0;0YThis  function  fetches  the file [11Xchanges.html[111X from the package's home page,
  extracts  the  times of changes for the data files in question, and compares
  them  with  the times of the last changes of the local data files. For that,
  the  [5XGAP[105X  package [5XIO[105X [Neu14] is needed; if it is not available then an error
  message is printed, and [9Xfail[109X is returned.[133X
  
  [33X[0;0YIf  the time of the last modification of a server file is later than that of
  the  local  copy  then  the  local  file  must  be updated. (This means that
  [10Xtouch[110Xing files in the local directories will cheat this function.)[133X
  
  [33X[0;0YIt  is  useful  that  a  system  administrator  (i. e.,  someone who has the
  permission  to  remove  files  from the data directories) runs this function
  from  time  to  time,  and  afterwards removes the files in the list that is
  returned.   This   way,   new  versions  of  these  files  will  be  fetched
  automatically from the servers when a user asks for their data.[133X
  
  
  [1X4.3 [33X[0;0YUser Parameters for the [5XAtlasRep[105X[101X[1X Package[133X[101X
  
  [33X[0;0YThis section lists global parameters for which it might make sense to change
  their     defaults    by    assignments    to    global    variables    (see
  [2XAtlasOfGroupRepresentationsUserParameters[102X  ([14X4.3-8[114X)  for an overview of these
  parameters)  or  using  [5XGAP[105X's  user preferences (see [14X'Reference: Configuring
  User preferences'[114X).[133X
  
  
  [1X4.3-1 [33X[0;0YLocal or Remote Access[133X[101X
  
  [33X[0;0YThere are two possibilities to use the [5XAtlasRep[105X package.[133X
  
  [8X[13XLocal access only (offline)[113X[108X
        [33X[0;6YYou  can  restrict  the access to the data that are actually stored in
        the local installation of [5XGAP[105X.[133X
  
  [8X[13XRemote access (online)[113X[108X
        [33X[0;6YIf your computer is connected to a network that provides access to the
        [5XATLAS[105X  data  (for  example  the  internet)  then  the functions of the
        package may fetch the requested data automatically from remote servers
        when  they  are  required  for  the first time; these data are then by
        default  stored  in  the  local copy, so later access to them needs no
        network transfer.[133X
  
  [33X[0;0YThe  latter  possibility  is presently not used by other [5XGAP[105X packages, so it
  may  be  regarded as an important feature of the [5XAtlasRep[105X package. Anyhow it
  requires a few words of explanation.[133X
  
  [33X[0;0YThe  possibility  of  online access reflects in particular the fact that the
  [5XATLAS[105X  of  Group  Representations  is  designed  as  an [13Xopen database[113X, it is
  expected  to  grow.  As  soon  as  the  developers  of  the  [5XATLAS[105X  of Group
  Representations  add  new  information  to  the  servers,  these data become
  available  in  [5XGAP[105X  when remote access is enabled, after one has updated the
  corresponding table of contents (see Section [14X4.2[114X).[133X
  
  [33X[0;0YRemote access is enabled if and only if the value of the [10Xremote[110X component of
  the  global variable [2XAtlasOfGroupRepresentationsInfo[102X ([14X7.1-6[114X) is [9Xtrue[109X. If one
  wants  to  work offline, i.e., if one does [13Xnot[113X want [5XGAP[105X to attempt accessing
  remote data then this value must be set to [9Xfalse[109X.[133X
  
  [33X[0;0YConversely,  if  the  default  value  of  the  [10Xremote[110X  component in your [5XGAP[105X
  installation  is  [9Xfalse[109X  then  changing  this  value  to  [9Xtrue[109X  may  be  not
  successful.  First,  it  might  be the case that no server is reachable. And
  second,  if  one can in principle [13Xdownload[113X files from a server then it might
  be  impossible  to actually [13Xstore[113X these files in the data directories of the
  installed  package;  in  this  case,  it  is  advisable to install the whole
  package or just its data directories in a private directory, see [14X'Reference:
  GAP Root Directories'[114X for details.[133X
  
  
  [1X4.3-2 [33X[0;0YAdding and Removing Servers[133X[101X
  
  [33X[0;0YWhen access to remote data is enabled (see Section [14X4.3-1[114X) then the available
  servers   are  given  by  the  [10Xservers[110X  component  of  the  global  variable
  [2XAtlasOfGroupRepresentationsInfo[102X ([14X7.1-6[114X).[133X
  
  [33X[0;0Y[13XRemoving[113X entries from this list means to disable access to the corresponding
  servers, [13Xadding[113X entries makes the corresponding servers available. Of course
  the  latter makes sense only if the new servers really exist, for example in
  a local network.[133X
  
  [33X[0;0YCurrently  there  is just one remote server. As soon as other servers become
  available,  or  a  server name is changed which makes it necessary to adjust
  the  [10Xservers[110X  component,  this  will  be  announced  in  the  [5XGAP[105X Forum, cf.
  [14X'Tutorial:  Further  Information about GAP'[114X. The same holds when upgrades of
  the package become available.[133X
  
  
  [1X4.3-3 [33X[0;0YAccessing Data Files with the [5XGAP[105X[101X[1X Package [5XIO[105X[101X[1X or with [11Xwget[111X[101X[1X[133X[101X
  
  [33X[0;0YWhen  access  to  remote  data is enabled (see Section [14X4.3-1[114X) then one needs
  either the [5XGAP[105X package [5XIO[105X [Neu14] or the external program [11Xwget[111X for accessing
  data files.[133X
  
  [33X[0;0YThe  chosen  alternative  is given by the value of the [10Xwget[110X component of the
  global variable [2XAtlasOfGroupRepresentationsInfo[102X ([14X7.1-6[114X).[133X
  
  [33X[0;0YIf  this  component has the value [9Xtrue[109X then only [11Xwget[111X is tried, if the value
  is [9Xfalse[109X then only the [5XIO[105X package is used. If this component is not bound or
  bound  to  another  value than [9Xtrue[109X or [9Xfalse[109X (this is also the default) then
  the  [5XIO[105X  package  is  preferred  to  [11Xwget[111X  if this package is available, and
  otherwise [11Xwget[111X is tried.[133X
  
  [33X[0;0YNote  that  the  system  program  [11Xwget[111X may be not available, and that it may
  require  some  work  to  install it; hints for that can be found on the home
  page of the [5XAtlasRep[105X package (see Section [14X4.4[114X).[133X
  
  
  [1X4.3-4 [33X[0;0YCompressed or Uncompressed Data Files[133X[101X
  
  [33X[0;0YWhen  used with UNIX, [5XGAP[105X can read [11Xgzip[111Xped files, see [14X'Reference: Saving and
  Loading     a     Workspace'[114X.     If     the     component    [10Xcompress[110X    of
  [2XAtlasOfGroupRepresentationsInfo[102X ([14X7.1-6[114X) has the value [9Xtrue[109X then each [5XMeatAxe[105X
  format  file  that  is fetched from a remote server is afterwards compressed
  with  [11Xgzip[111X.  This  saves  a  lot  of  space if many [5XMeatAxe[105X format files are
  accessed.  (Note  that  data  files  in  other  formats are very small.) For
  example,  at  the time of the release of version 1.5.1 there were about [22X8400[122X
  data  files  in  [5XMeatAxe[105X  format, which needed about [22X1400[122X MB in uncompressed
  text  format  and  about [22X275[122X MB in compressed text format. The default value
  for the component [10Xcompress[110X is [9Xfalse[109X.[133X
  
  
  [1X4.3-5 [33X[0;0YCustomizing [10XDisplayAtlasInfo[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  way  how  [2XDisplayAtlasInfo[102X  ([14X3.5-1[114X)  shows  the  requested  overview is
  controlled       by       the       component       [10XdisplayFunction[110X       of
  [2XAtlasOfGroupRepresentationsInfo[102X   ([14X7.1-6[114X).   The   default  value  is  [2XPrint[102X
  ([14XReference:  Print[114X),  other  useful values are [2XPrintFormattedString[102X ([14XGAPDoc:
  PrintFormattedString[114X)  and  [10XAGR.Pager[110X;  the  latter  calls [2XPager[102X ([14XReference:
  Pager[114X) with the [10Xformatted[110X option, which is necessary for switching off [5XGAP[105X's
  automatic line breaking.[133X
  
  
  [1X4.3-6 [33X[0;0YCustomizing the Access to Data Files[133X[101X
  
  [33X[0;0YBy  default,  local data files are stored in the subdirectories [11Xdatagens[111X and
  [11Xdataword[111X of the directory given by the user preference [10XAtlasRepDataDirectory[110X
  (see  Section  [14X4.3-9[114X),  and the files are exactly the text files provided on
  the servers. However, a more flexible approach may be useful.[133X
  
  [33X[0;0YFirst,  one  may want to use [13Xdifferent file formats[113X, for example the [5XMeatAxe[105X
  binary  files  that are provided by the servers parallel to the [5XMeatAxe[105X text
  files.  Second,  one  may  want  to use [13Xa different directory structure[113X, for
  example  the  same  structure  as  used on the servers –this makes sense for
  example  if  a  local  mirror of a server is available, because then one can
  read the server files directly, without transferring/copying them to another
  directory.[133X
  
  [33X[0;0YAs  a  consequence, one would like to customize the meaning of the following
  three access steps.[133X
  
  [8XAre the required files locally available?[108X
        [33X[0;6YThe  required files may have a different name or a different path, and
        the data can be available in one file or can be distributed to several
        files.[133X
  
  [8XHow can a file be made locally available?[108X
        [33X[0;6YA  different  server file may be fetched or some postprocessing may be
        required.[133X
  
  [8XHow is the data of a file accessed by [5XGAP[105X?[108X
        [33X[0;6YA different function may be needed to read the file.[133X
  
  [33X[0;0YDetails how to achieve these customizations can be found in Section [14X7.2[114X.[133X
  
  
  [1X4.3-7 [33X[0;0YReading Large Matrices over Finite Fields[133X[101X
  
  [33X[0;0YMatrices over finite fields in [5XGAP[105X can be represented in a compressed format
  that  needs  less  space  than  the  corresponding text file. Such a [5XMeatAxe[105X
  format  text file can be read by [2XScanMeatAxeFile[102X ([14X7.3-1[114X) either line by line
  (which  is  the  default) or as a whole; the latter is faster but needs more
  space  than  the  former.  For example, a [22X4370[122X by [22X4370[122X matrix over the field
  with  two  elements (as occurs for an irreducible representation of the Baby
  Monster)  requires less than [22X3[122X MB space in [5XGAP[105X but the corresponding [5XMeatAxe[105X
  format  text  file is more than [22X19[122X MB large, which means that when one reads
  the  file with the fast variant, [5XGAP[105X will temporarily grow by more than this
  value.   One   can   change   the   mode  by  setting  the  global  variable
  [2XCMeatAxe.FastRead[102X ([14X7.1-4[114X) to [9Xtrue[109X or [9Xfalse[109X, respectively.[133X
  
  [33X[0;0YNote  that this parameter is meaningful only when [2XScanMeatAxeFile[102X ([14X7.3-1[114X) is
  used.  It  has  no  effect  for  example  if  [5XMeatAxe[105X binary files are read,
  cf. [2XFFMatOrPermCMtxBinary[102X ([14X7.3-5[114X).[133X
  
  [1X4.3-8 AtlasOfGroupRepresentationsUserParameters[101X
  
  [29X[2XAtlasOfGroupRepresentationsUserParameters[102X(  ) [32X function
  
  [33X[0;0YThis  function  returns  a  string that describes an overview of the current
  values  of the user parameters introduced in this section. One can use [2XPrint[102X
  ([14XReference: Print[114X) or [2XPager[102X ([14XReference: Pager[114X) for showing the overview.[133X
  
  
  [1X4.3-9 [33X[0;0YUser preference [10XAtlasRepDataDirectory[110X[101X[1X[133X[101X
  
  [33X[0;0YThe value must be a string that is the filename of a directory (in the sense
  of   [2XIsDirectoryPath[102X   ([14XReference:   IsDirectoryPath[114X))   that  contains  the
  directories  [11Xdatagens[111X  and [11Xdataword[111X in which downloaded data will be stored.
  The  default  is  the installation path of the [5XAtlasRep[105X package (including a
  trailing slash symbol).[133X
  
  
  [1X4.3-10 [33X[0;0YUser preference [10XWriteMeatAxeFilesOfMode2[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  value  [9Xtrue[109X  means  that the function [2XMeatAxeString[102X ([14X7.3-2[114X) will encode
  permutation  matrices  via  mode 2 descriptions, that is, the first entry in
  the  header  line is 2, and the following lines contain the positions of the
  nonzero  entries.  If  the  value  is [9Xfalse[109X (the default) then [2XMeatAxeString[102X
  ([14X7.3-2[114X) encodes permutation matrices via mode 1 or mode 6 descriptions, that
  is, the lines contain the matrix entries.[133X
  
  
  [1X4.3-11 [33X[0;0YUser preference [10XBaseOfMeatAxePermutation[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  value  [22X0[122X  means  that the function [2XCMtxBinaryFFMatOrPerm[102X ([14X7.3-4[114X) writes
  zero-based  permutations,  that is, permutations acting on the points from [22X0[122X
  to the degree minus one; this is achieved by shifting down all images of the
  [5XGAP[105X permutation by one. The value [22X1[122X (the default) means that the permutation
  stored in the binary file acts on the points from [22X1[122X to the degree.[133X
  
  [33X[0;0YUp to version 2.3 of the [10XC[110X-[5XMeatAxe[105X, permutations in binary files were always
  one-based.  Zero-based  permutations  were  introduced in version 2.4, which
  still is able to read files containing one-based permutations.[133X
  
  
  [1X4.4 [33X[0;0YWeb Services for the [5XAtlasRep[105X[101X[1X Package[133X[101X
  
  [33X[0;0YThe home page of the [5XAtlasRep[105X package is[133X
  
  [33X[0;0Y[7Xhttp://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep[107X.[133X
  
  [33X[0;0YBesides package archives and introductory package information, it provides[133X
  
  [30X    [33X[0;6Ythe  current  file with the [13Xtable of contents[113X (the file [11Xgap/atlasprm.g[111X
        of                  the                  package,                  see
        [7Xhttp://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/atlasprm.g[107X),
        cf. [2XReloadAtlasTableOfContents[102X ([14X4.2-1[114X),[133X
  
  [30X    [33X[0;6Ya  [13Xstarter  archive[113X containing many small representations and programs
        (see
        [7Xhttp://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/atlasrepdata.tar.gz[107X),[133X
  
  [30X    [33X[0;6Ythe   list   of   [13Xchanges   of   server  files[113X  in  HTML  format  (see
        [7Xhttp://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/htm/data/changes.htm[107X),
        cf. [2XAtlasOfGroupRepresentationsTestTableOfContentsRemoteUpdates[102X
        ([14X4.2-4[114X), and[133X
  
  [30X    [33X[0;6Yan  [13Xoverview  of the data[113X available via the [5XGAP[105X interface to the [5XATLAS[105X
        of      Group     Representations,     in     HTML     format     (see
        [7Xhttp://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/htm/data/overview.htm[107X);
        this  is similar to the information shown by [2XDisplayAtlasInfo[102X ([14X3.5-1[114X),
        further  information  can  be found on the home page of the [5XATLAS[105X, see
        [7Xhttp://brauer.maths.qmul.ac.uk/Atlas[107X.[133X
  
  
  [1X4.5 [33X[0;0YExtending the [5XATLAS[105X[101X[1X Database[133X[101X
  
  [33X[0;0YUsers  who  have  computed new representations that might be interesting for
  inclusion  into  the  [5XATLAS[105X  of  Group  representations can send the data in
  question to [7Xmailto:R.A.Wilson@qmul.ac.uk[107X.[133X
  
  [33X[0;0YIt  is  also possible to store [21Xprivate[121X representations and programs in local
  directories,  and  to  use  them  in  the same way as the [21Xofficial[121X data. See
  Chapter [14X5[114X for details.[133X
  
