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


dgmap, dgpart - compute static mappings and partitions in parallel


dgmap [options] [gfile] [tfile] [mfile] [lfile]


The dgmap program computes, in a parallel way, a static mapping of a source graph onto a target graph.

The dgpart program is a simplified interface to dgmap, which performs graph partitioning instead of static mapping. Consequently, the desired number of parts has to be provided, in lieu of the target architecture. When using the program for graph clustering, the number of parts turns into maximum cluster weight.

The -b and -c option?s allow the user to set preferences on the behavior of the mapping strategy which is used by default. The -m option allows the user to define a custom mapping strategy.

The -q option turns the programs into graph clustering programs. In this case, dgmap only accepts variable-sized target architectures.

Source graph file gfile is either a centralized graph file, or a set of files representing fragments of a distributed graph. For dgmap, the target architecture file tfile describes either algorithmically-coded topologies such as meshes and hypercubes, or decomposition-defined architectures created by means of the amk_grf(1) program. See gmap(1) for a description of target architectures. The resulting mapping is stored in file mfile. 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 '-'.


dgmap and dgpart base on implementations of the MPI interface to spread work across the processing elements. They are therefore not likely to be run directly, but instead through some launcher command such as mpirun.


Set maximum load imbalance ratio for graph partitioning or static mapping. When programs are used as clustering tools, this parameter sets the maximum load imbalance ratio for recursive bipartitions. Exclusive with the -m option.
Choose default mapping strategy according to one or several option?s among:
enforce load balance as much as possible.
privilege quality over speed (default).
privilege speed over quality.
enforce safety.
enforce scalability.

It is exclusive with the -m option.

Display some help.
Use parallel mapping strategy strat (see PT-Scotch user's manual for more information).
(for dgpart)
(for dgmap) Use the programs as graph clustering tools instead of static mapping or graph partitioning tools. For dgpart, the number of parts will become the maximum cluster weight. For dgmap, this number pwght has to be passed after the option.
Set root process for centralized files (default is 0).
Display program version and copyright.
mapping information.
strategy information.
timing information.


At the time being (version 5.1), dgmap cannot compute full static mappings as gmap(1) does, but only partitions (that is, mappings onto unweighted or weighted complete graphs). Target architectures other than the 'cmplt' and 'wcmplt' ones will lead to an error message.


Run dgpart on 5 processing elements to compute a partition into 7 parts of graph brol.grf and save the resulting ordering to file

$ mpirun -np 5 dgpart 7 brol.grf
Run dgpart on 5 processing elements to partition into 7 parts the distributed graph stored on graph fragment files brol5-0.dgr to brol5-4.dgr, and save the resulting mapping to file (see dgscat(1) for an explanation of the '%p' and '%r' sequences in names of distributed graph fragments).

$ mpirun -np 5 dgpart 7 brol%p-%r.dgr


dgtst(1), dgscat(1), amk_grf(1), acpl(1), gmap(1), gmtst(1).

PT-Scotch user's manual.


Francois Pellegrini <>

23 November 2019