  
  [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
  somewhere  else,  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;0YIf  it  is  likely that you 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.[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 [14X4.2-2[114X, the
  defaults  are  the  subdirectories  [11Xdata*[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 Apr 12 12:34 dataext[128X[104X
    [4X[28Xdrwxrwxrwt   3 you      you          1024 Apr 12 12:34 datagens[128X[104X
    [4X[28Xdrwxrwxrwt   3 you      you          1024 Apr 12 12:34 datapkg[128X[104X
    [4X[28Xdrwxrwxrwt   3 you      you          1024 Apr 12 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;0YPDF,  HTML, and text versions of the package manual are available in the [11Xdoc[111X
  directory of the package.[133X
  
  
  [1X4.2 [33X[0;0YUser Preferences of the [5XAtlasRep[105X[101X[1X Package[133X[101X
  
  [33X[0;0YThis  section  describes  global parameters for which it might make sense to
  change  their  defaults,  using  [5XGAP[105X's  user  preferences  (see  [14X'Reference:
  Configuring User preferences'[114X).[133X
  
  [30X    [33X[0;6YIs access to remote data allowed (see Section [14X4.2-1[114X)? If yes then also
        the following parameters are of interest.[133X
  
        [30X    [33X[0;12YFrom where can the data be fetched (see Section [14X4.2-3[114X)?[133X
  
        [30X    [33X[0;12YWhere are local copies of these data stored (see Section [14X4.2-2[114X)?[133X
  
        [30X    [33X[0;12YShall  files  be compressed after they have been downloaded (see
              Section [14X4.2-4[114X)?[133X
  
  [30X    [33X[0;6YThe following parameters influence reading and writing of local files.[133X
  
        [30X    [33X[0;12YWhat  shall  actually  happen  when  data  are  requested by the
              interface functions (see Section [14X4.2-5[114X)?[133X
  
        [30X    [33X[0;12YIf the value of the user preference [10XFileAccessFunctions[110X contains
              [10X"direct access to a local server"[110X, what is its path (see Section
              [14X4.2-6[114X)?[133X
  
        [30X    [33X[0;12YShall [2XScanMeatAxeFile[102X ([14X7.3-1[114X) focus on small runtime or on small
              space when reading [5XMeatAxe[105X text files (see Section [14X4.2-7[114X)?[133X
  
        [30X    [33X[0;12YWhich  kind  of  headers shall [2XMeatAxeString[102X ([14X7.3-2[114X) create (see
              Section [14X4.2-8[114X)?[133X
  
        [30X    [33X[0;12YShall  [2XMeatAxeString[102X ([14X7.3-2[114X) interpret permutation matrices more
              as  permutations  (mode  2)  or  as  matrices (mode 1 or 6) (see
              Section [14X4.2-9[114X)?[133X
  
        [30X    [33X[0;12YShall  the default for [2XCMtxBinaryFFMatOrPerm[102X ([14X7.3-4[114X) be to write
              binary  files  of  zero-based  or  one-based  permutations  (see
              Section [14X4.2-10[114X)?[133X
  
  [30X    [33X[0;6YWhich function is used by [2XDisplayAtlasInfo[102X ([14X3.6-1[114X) for printing to the
        screen (see Section [14X4.2-11[114X)?[133X
  
  [30X    [33X[0;6YHow  does [2XDisplayAtlasInfo[102X ([14X3.6-1[114X) mark data that do not belong to the
        core database (see Section [14X4.2-12[114X)?[133X
  
  [30X    [33X[0;6YShall  debug  messages  be printed when local data files are read (see
        Section [14X4.2-13[114X)?[133X
  
  
  [1X4.2-1 [33X[0;0YUser preference [10XAtlasRepAccessRemoteFiles[110X[101X[1X[133X[101X
  
  [33X[0;0YThe value [9Xtrue[109X (the default) allows the [5XAtlasRep[105X package to fetch data files
  that  are  not  yet locally available. If the value is [9Xfalse[109X then only those
  data files can be used that are available locally.[133X
  
  [33X[0;0YIf you are working offline then you should set the value to [9Xfalse[109X.[133X
  
  [33X[0;0YChanging  the value in a running [5XGAP[105X session does not affect the information
  shown  by [2XDisplayAtlasInfo[102X ([14X3.6-1[114X), this information depends on the value of
  the preference at the time when the [5XAtlasRep[105X package and its data extensions
  get loaded.[133X
  
  
  [1X4.2-2 [33X[0;0YUser preference [10XAtlasRepDataDirectory[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  value  must  be  a  string  that  is  either empty or the filename of a
  directory  (in  the  sense  of [2XIsDirectoryPath[102X ([14XReference: IsDirectoryPath[114X))
  that contains the directories in which downloaded data will be stored.[133X
  
  [33X[0;0YAn  empty string means that downloaded data are just kept in the [5XGAP[105X session
  but not saved to local files.[133X
  
  [33X[0;0YIn  the  following  situations, a nonempty default value is computed. If the
  current  [5XGAP[105X  session  is  running  inside  a  [5XJulia[105X  session  then  a [5XJulia[105X
  scratchspace  is  taken. Otherwise, if the subdirectories [11Xdataext[111X, [11Xdatagens[111X,
  [11Xdataword[111X  of  the  [5XAtlasRep[105X  directory  are  writable  for the user then the
  installation  path  of  the  [5XAtlasRep[105X  package  (including  a trailing slash
  symbol) is taken. In all other cases, the default is an empty string.[133X
  
  
  [1X4.2-3 [33X[0;0YUser preference [10XAtlasRepTOCData[110X[101X[1X[133X[101X
  
  [33X[0;0YThe value must be a list of strings of the form [10X"ID|address"[110X where [10XID[110X is the
  id  of  a  part  of the database and [10Xaddress[110X is an URL or a file path (as an
  absolute  path  or  relative  to  the  user's  home directory, cf. [2XDirectory[102X
  ([14XReference:  Directory[114X))  of  a  readable JSON format file that contains the
  table of contents of this part, see [2XStringOfAtlasTableOfContents[102X ([14X5.1-3[114X).[133X
  
  [33X[0;0YThe default lists four entries: the core database, the data distributed with
  the  [5XAtlasRep[105X  package,  and  the  data that belong to the packages [5XMFER[105X and
  [5XCTBlocks[105X.[133X
  
  
  [1X4.2-4 [33X[0;0YUser preference [10XCompressDownloadedMeatAxeFiles[110X[101X[1X[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    package's    user    preference
  [10XCompressDownloadedMeatAxeFiles[110X  has  the value [9Xtrue[109X then each [5XMeatAxe[105X format
  text file that is downloaded from the internet is afterwards compressed with
  [11Xgzip[111X. The default value is [9Xfalse[109X.[133X
  
  [33X[0;0YCompressing  files  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 2.0 the core database
  contained  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.[133X
  
  
  [1X4.2-5 [33X[0;0YUser preference [10XFileAccessFunctions[110X[101X[1X[133X[101X
  
  [33X[0;0YThis  preference allows one to customize what actually happens when data are
  requested  by  the  interface  functions:  Is  it necessary to download some
  files?  If  yes  then which files are downloaded? If no then which files are
  actually read into [5XGAP[105X?[133X
  
  [33X[0;0YCurrently one can choose among the following features.[133X
  
  [31X1[131X   [33X[0;6YDownload/read [5XMeatAxe[105X text files.[133X
  
  [31X2[131X   [33X[0;6YPrefer downloading/reading [5XMeatAxe[105X binary files.[133X
  
  [31X3[131X   [33X[0;6YPrefer reading locally available data files.[133X
  
  [33X[0;0Y(Of   course   files   can   be  downloaded  only  if  the  user  preference
  [10XAtlasRepAccessRemoteFiles[110X has the value [9Xtrue[109X, see Section [14X4.2-1[114X.)[133X
  
  [33X[0;0YThis  feature  could  be  used more generally, see Section [14X7.2[114X for technical
  details and the possibility to add other features.[133X
  
  
  [1X4.2-6 [33X[0;0YUser preference [10XAtlasRepLocalServerPath[110X[101X[1X[133X[101X
  
  [33X[0;0YIf  the data of the core database are available locally (for example because
  one  has  access  to a local mirror of the data) then one may prefer reading
  these  files  instead of downloading data. In order to achieve this, one can
  set  the user preference [10XAtlasRepLocalServerPath[110X and add [10X"direct access to a
  local server"[110X to the user preference [10XFileAccessFunctions[110X, see Section [14X4.2-5[114X.[133X
  
  [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 data of
  the  [5XATLAS[105X of Group Representations, in the same directory tree structure as
  on the [5XATLAS[105X server.[133X
  
  
  [1X4.2-7 [33X[0;0YUser preference [10XHowToReadMeatAxeTextFiles[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  value  [10X"fast"[110X  means  that [2XScanMeatAxeFile[102X ([14X7.3-1[114X) reads text files via
  [2XStringFile[102X  ([14XGAPDoc:  StringFile[114X).  Otherwise  each file containing a matrix
  over a finite field is read line by line via [2XReadLine[102X ([14XReference: ReadLine[114X),
  and   the   [5XGAP[105X  matrix  is  constructed  line  by  line,  in  a  compressed
  representation    (see [14X'Reference:   Row   Vectors   over   Finite   Fields'[114X
  and [14X'Reference:  Matrices  over  Finite  Fields'[114X); this makes it possible to
  read large matrices in a reasonable amount of space.[133X
  
  [33X[0;0YThe  [2XStringFile[102X  ([14XGAPDoc:  StringFile[114X)  approach  is  faster  but needs more
  intermediate  space  when  text files containing matrices over finite fields
  are  read.  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. This means that when one reads the file
  with the fast variant, [5XGAP[105X will temporarily grow by more than this value.[133X
  
  [33X[0;0YNote  that this parameter has an effect 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
  
  
  [1X4.2-8 [33X[0;0YUser preference [10XWriteHeaderFormatOfMeatAxeFiles[110X[101X[1X[133X[101X
  
  [33X[0;0YThis  user  preference  determines the format of the header lines of [5XMeatAxe[105X
  format   strings   created  by  [2XMeatAxeString[102X  ([14X7.3-2[114X),  see  the  [10XC[110X-[5XMeatAxe[105X
  manual [Rin] for details. The following values are supported.[133X
  
  [8X[10X"numeric"[110X[8X[108X
        [33X[0;6Ymeans  that  the  header  line of the returned string consists of four
        integers  (in  the case of a matrix these are mode, row number, column
        number and field size),[133X
  
  [8X[10X"numeric (fixed)"[110X[8X[108X
        [33X[0;6Ymeans  that  the  header  line of the returned string consists of four
        integers  as  in  the case [10X"numeric"[110X, but additionally each integer is
        right aligned in a substring of length (at least) six,[133X
  
  [8X[10X"textual"[110X[8X[108X
        [33X[0;6Ymeans  that  the  header  line  of  the  returned  string  consists of
        assignments such as [10Xmatrix field=2[110X.[133X
  
  
  [1X4.2-9 [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
  
  
  [1X4.2-10 [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.[133X
  
  
  [1X4.2-11 [33X[0;0YUser preference [10XDisplayFunction[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  way  how  [2XDisplayAtlasInfo[102X  ([14X3.6-1[114X)  shows  the  requested  overview is
  controlled  by  the  package [5XAtlasRep[105X's user preference [10XDisplayFunction[110X. The
  value  must  be a string that evaluates to a [5XGAP[105X function. The default value
  is   [10X"Print"[110X  (see  [2XPrint[102X  ([14XReference:  Print[114X)),  other  useful  values  are
  [10X"PrintFormattedString"[110X        (see       [2XPrintFormattedString[102X       ([14XGAPDoc:
  PrintFormattedString[114X))   and   [10X"AGR.Pager"[110X;  the  latter  means  that  [2XPager[102X
  ([14XReference:  Pager[114X)  is called with the [10Xformatted[110X option, which is necessary
  for switching off [5XGAP[105X's automatic line breaking.[133X
  
  
  [1X4.2-12 [33X[0;0YUser preference [10XAtlasRepMarkNonCoreData[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  value  is  a  string  (the  default  is  a  star  '*')  that is used in
  [2XDisplayAtlasInfo[102X  ([14X3.6-1[114X)  to  mark  data  that  do  not  belong to the core
  database, see Section  [14X5.2[114X.[133X
  
  
  [1X4.2-13 [33X[0;0YUser preference [10XDebugFileLoading[110X[101X[1X[133X[101X
  
  [33X[0;0YIf  the  value is [9Xtrue[109X then debug messages are printed before and after data
  files get loaded. The default value is [9Xfalse[109X.[133X
  
  
  [1X4.2-14 [33X[0;0YUser preference [10XAtlasRepJsonFilesAddresses[110X[101X[1X[133X[101X
  
  [33X[0;0YThe  value,  if  set, must be a list of length two, the first entry being an
  URL  describing a directory that contains Json format files of the available
  matrix  representations  in  characteristic  zero,  and  the  second being a
  directory  path  where  these files shall be stored locally. If the value is
  set  (this  is  the  default) then the functions of the package use the Json
  format files instead of the GAP format files.[133X
  
  
  [1X4.3 [33X[0;0YWeb Contents for the [5XAtlasRep[105X[101X[1X Package[133X[101X
  
  [33X[0;0YThe        home        page        of       the       [5XAtlasRep[105X       package
  ([7Xhttps://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep[107X) provides[133X
  
  [30X    [33X[0;6Ypackage archives,[133X
  
  [30X    [33X[0;6Yintroductory package information,[133X
  
  [30X    [33X[0;6Ythe  current  [13Xtable of contents[113X of core data in the file [11Xatlasprm.json[111X
        ([7Xhttps://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/atlasprm.json[107X)
        of the package, cf. [2XStringOfAtlasTableOfContents[102X ([14X5.1-3[114X),[133X
  
  [30X    [33X[0;6Ythe     list    of    changes    of    remote    core    data    files
        ([7Xhttps://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/htm/data/changes.htm[107X),[133X
  
  [30X    [33X[0;6Ya                            starter                           archive
        ([7Xhttps://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/atlasrepdata.tar.gz[107X)
        containing many small representations and programs, and[133X
  
  [30X    [33X[0;6Yan          overview          of         the         core         data
        ([7Xhttps://www.math.rwth-aachen.de/~Thomas.Breuer/atlasrep/htm/data[107X)  in
        a   similar   format   as   the  information  shown  by  the  function
        [2XDisplayAtlasInfo[102X  ([14X3.6-1[114X) of the package; more details can be found on
        the    home    page    of   the   [5XATLAS[105X   of   Group   Representations
        ([7Xhttp://atlas.math.rwth-aachen.de/Atlas/v3[107X).[133X
  
  
  [1X4.4 [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  make  additional  representations  and  programs
  accessible  for the [5XGAP[105X interface, and to use these [21Xprivate[121X data in the same
  way as the core data. See Chapter [14X5[114X for details.[133X
  
