scotch_gmap - Online in the Cloud

PROGRAM:

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 options 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', on input only).

OPTIONS

-bval 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.

-copt Choose default mapping 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.

It is exclusive with the -m option.

-h Display some help.

-mstrat
Use sequential mapping strategy strat (see Scotch user's manual for more
information).

-q (for gpart)

-qpwght
(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.

-V Display program version and copyright.

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

m mapping information.

s strategy information.

t 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:

cmplt dim
unweighted complete graph of size dim.

cmpltw dim w0 w1 ... wdim-1
weighted complete graph of size size and of respective loads w0, w1, ..., wdim-1.

hcub dim
hypercube of dimension dim.

leaf hgt n0 w0 ... nhgt-1 whgt-1
tree-leaf graph of height hgt with (n0 times n1 times ... nhgt-1) vertices, with
inter-cluster link weights of w0, w1, ... whgt-1.

mesh2D dimX dimY
2D mesh of dimX times dimY nodes.

mesh3D dimX dimY dimZ
23 mesh of dimX times dimY times dimZ nodes.

torus2D dimX dimY
2D torus of dimX times dimY nodes.

torus3D dimX dimY dimZ
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

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