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gmap(1) Scotch user's manual gmap(1)

NAME

gmap, gpart - compute static mappings and partitions sequentially

SYNOPSIS

gmap [options] [gfile] [tfile] [mfile] [lfile]
gpart [options] [nparts/pwght] [gfile] [mfile] [lfile]

DESCRIPTION

The gmap program computes, in a sequential way, a static mapping of a source graph onto a target graph.

The gpart program is a simplified interface to gmap, 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, gmap only accepts variable-sized target architectures.

Source graph file gfile can only be a centralized graph file. For gmap, 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. 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 '-'.

When the proper libraries have been included at compile time, gmap and gpart 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').

OPTIONS

-b?val
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.

It is exclusive with the -m option.

Display some help.
-m?strat
Use sequential mapping strategy strat (see Scotch user's manual for more information).
-q
(for gpart)
-q?pwght
(for gmap) Use the programs as graph clustering tools instead of static mapping or graph partitioning tools. For gpart, the number of parts will become the maximum cluster weight. For gmap, this number pwght has to be passed after the option.
Display program version and copyright.
Set verbose mode to verb. It is a set of one of more characters which can be:
mapping information.
strategy information.
timing information.

TARGET ARCHITECTURES

Target architectures represent graphs onto which source graphs are mapped. In order to speed-up the obtainment of target architecture topological properties during the computation of mappings, some classical topologies are algorithmically coded into the mapper itself. These topologies are consequently simply defined by their code name, followed by their dimensional parameters:

unweighted complete graph of size dim.
weighted complete graph of size size and of respective loads w0, w1, ..., wdim-1.
hypercube of dimension dim.
tree-leaf graph of height hgt with (n0 times n1 times ... nhgt-1) vertices, with inter-cluster link weights of w0, w1, ... whgt-1.
2D mesh of dimX times dimY nodes.
23 mesh of dimX times dimY times dimZ nodes.
2D torus of dimX times dimY nodes.
3D torus of dimX times dimY times dimZ nodes.

Other target topologies can be created from their source graph description by using the amk_grf(1) command. In this case, the target description will begin with the code name deco.

MAPPINGS

Mappings are represented by as many lines as there are vertices in the source graph. Each of these lines is made of two figures: the number of the vertex (or its label if source graph vertices are labeled) and the index of the target vertex to which it has been assigned. Target vertex indices range from 0 to the number of vertices in the target architecture (that is, the number of parts) minus one.

This block of lines is always preceded by the number of such lines. In most cases, since full mappings are requested, the number of lines is equal to the number of vertices in the source graph.

EXAMPLES

Run gpart to compute a partition into 7 parts of graph 'brol.grf' and save the resulting ordering to file 'brol.map'.



    $ gpart 7 brol.grf brol.map
Run gmap to compute a partition, into 3 parts of respective weights 1, 2 and 4, of graph 'brol.grf' and save the resulting mapping to file 'brol.map'. The dash '-' standard file name is used so that the target architecture description is read from the standard input, through the pipe, as provided by the 'echo' shell command. 



    $ echo "cmpltw 3 1 2 4" | gmap brol.grf - brol.map

SEE ALSO

amk_grf(1), acpl(1), gmtst(1), dgmap(1).

Scotch user's manual.

AUTHOR

Francois Pellegrini <francois.pellegrini@labri.fr>

23 November 2019