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ptscotch_dgscat(1)     PT-Scotch user's manual    ptscotch_dgscat(1)

       ptscotch_dgscat  -  build distributed source graph file frag‐
       ments from a centralized source graph file

       ptscotch_dgscat [options] [igfile] [ogfile]

       The ptscotch_dgscat program reads a centralized source  graph
       igfile  and  writes  it  back  on  the form of a set of files
       ogfile representing fragments of a distributed source graph.

       When file names are not specified, data is read from standard
       input  and  written  to standard output. Standard streams can
       also be explicitly represented by a dash '-'.

       When the proper libraries have been included at compile time,
       dgord  can  directly  handle compressed graphs, both as input
       and output. A stream is treated as  compressed  whenever  its
       name  is  postfixed with a compressed file extension, such as
       in 'brol.grf.bz2' or '-.gz'. The  compression  formats  which
       can be supported are the bzip2 format ('.bz2'), the gzip for‐
       mat ('.gz'), and the lzma format ('.lzma', on input only).

       dgord bases on implementations of the MPI interface to spread
       work  across  the  processing  elements.  It is therefore not
       likely to be run directly, but instead through some  launcher
       command such as mpirun.

       In  order to tell whether programs should read from, or write
       to, a single file located on only one processor, or to multi‐
       ple  instances  of the same file on all of the processors, or
       else to distinct files on each of the processors,  a  special
       grammar  has  been designed, which is based on the '%' escape
       character. Four such escape sequences are defined, which  are
       interpreted  independently  on every processor, prior to file
       opening. By default, when  a  filename  is  provided,  it  is
       assumed that the file is to be opened on only one of the pro‐
       cessors, called the root processor, which is usually  process
       $0$  of the communicator within which the program is run. The
       index of the root processor can be changed by means of the -r
       option.  Using  any of the first three escape sequences below
       will instruct programs to open in parallel  a  file  of  name
       equal  to  the  interpreted  filename,  on every processor on
       which they are run.

       %p     Replaced by the number of processes in the global com‐
              municator in which the program is run. Leads to paral‐
              lel opening.

       %r     Replaced on each process running the  program  by  the
              rank of this process in the global communicator. Leads
              to parallel opening.

       %-     Discarded,  but  leads  to  parallel   opening.   This
              sequence  is  mainly used to instruct programs to open
              on every processor  a  file  of  identical  name.  The
              opened  files can be, according whether the given path
              leads to a shared directory or to directories that are
              local to each processor, either to the opening of mul‐
              tiple instances of the same file, or to the opening of
              distinct  files  which  may each have a different con‐
              tent, respectively (but in this latter case it is much
              recommended  to  identify  files  by means of the '%r'

       %%     Replaced by a single '%' character. File  names  using
              this  escape  sequence are not considered for parallel
              opening, unless one or  several  of  the  three  other
              escape sequences are also present.

For  instance,  filename  'brol'  will  lead  to the opening of file
'brol' on the  root  processor  only,  filename  '%-brol'  (or  even
'br%-ol')  will  lead to the parallel opening of files called 'brol'
on every processor, and filename 'brol%p-%r' will lead to the  open‐
ing of files on which the program were to run.

       -c     Check  the consistency of the input source graph after
              loading it into memory.

       -h     Display some help.

       -rpnum Set root process for centralized files (default is 0).

       -V     Display program version and copyright.

       Run ptscotch_dgscat on 5 processing elements to scatter  cen‐
       tralized  graph  file  brol.grf into 5 gzipped file fragments
       brol5-0.grf.gz to brol5-4.grf.gz.

             $ mpirun -np 5 ptscotch_dgscat brol.grf brol%p-%r.grf.gz

       ptscotch_dgtst(1), ptscotch_dgord(1), scotch_gmk_hy(1).

       PT-Scotch user's manual.

       Francois Pellegrini <>

                            June 05, 2008         ptscotch_dgscat(1)
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