NAME

       dgord - compute sparse matrix orderings of graphs in parallel

SYNOPSIS

       dgord [options] [gfile] [ofile] [lfile]

DESCRIPTION

       The  dgord  program  computes,  in  a  parallel  way, an ordering of a Scotch source graph
       representing the pattern of some symmetric sparse matrix.

       Source graph file gfile is either a centralized graph file, or a set of files representing
       fragments of a distributed graph. The resulting ordering is stored in file ofile. Eventual
       logging information (such as the one produced by option -v) is sent to  file  lfile.  When
       file  names  are  not  specified, data is read from standard input and written to standard
       output. Standard streams can also be explicitely 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 format ('.gz'), and the lzma format ('.lzma').

       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.

OPTIONS

       -copt  Choose default ordering strategy according to one or several options among:

              b      enforce load balance as much as possible.

              q      privilege quality over speed (default).

              s      privilege speed over quality.

              t      enforce safety.

              x      enforce scalability.

       -h     Display some help.

       -mmfile
              Save column block mapping data to file mfile.  Mapping  data  specifies,  for  each
              vertex, the index of the column block to which this vertex belongs.

       -ostrat
              Use  parallel  graph  ordering strategy strat (see PT-Scotch user's manual for more
              information).

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

       -ttfile
              Save partitioning tree data to file tfile. Partitioning tree  data  specifies,  for
              each  vertex,  the  index  of  the first vertex of the parent block of the block to
              which the vertex belongs. Altogether with the mapping data provided in file  mfile,
              it allows one to rebuild the separator tree of the nested dissection process.

       -V     Display program version and copyright.

       -vverb Set verbose mode to verb. It is a set of one of more characters which can be:

              s      strategy information.

              t      timing information.

EXAMPLES

       Run dgord on 5 processing elements to reorder matrix graph brol.grf and save the resulting
       ordering to file brol.ord, using the default sequential graph ordering strategy:

           $ mpirun -np 5 dgord brol.grf brol.ord

       Run dgord on 5 processing elements to reorder  the  distributed  matrix  stored  on  graph
       fragment  files  brol5-0.dgr  to  brol5-4.dgr,  and  save  the  resulting ordering to file
       brol.ord (see dgscat(1) for an explanation of the '%p' and  '%r'  sequences  in  names  of
       distributed graph fragments).

           $ mpirun -np 5 dgord brol%p-%r.dgr brol.ord

SEE ALSO

       dgtst(1), dgscat(1), gmk_hy(1), gord(1).

       PT-Scotch user's manual.

AUTHOR

       Francois Pellegrini <francois.pellegrini@labri.fr>

                                         23 November 2019                                dgord(1)