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Recent versions of scotch are rarely available in packaged form for ready installation on GNU/Linux distributions and so the sources are generally required.
118 lines
4.2 KiB
Groff
118 lines
4.2 KiB
Groff
." Text automatically generated by txt2man
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.TH dgscat 1 "August 03, 2010" "" "PT-Scotch user's manual"
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.SH NAME
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\fBdgscat \fP- build distributed source graph file fragments from a centralized source graph file
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\fB
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.SH SYNOPSIS
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.nf
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.fam C
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\fBdgscat\fP [\fIoptions\fP] [\fIigfile\fP] [\fIogfile\fP]
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.fam T
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.fi
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.SH DESCRIPTION
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The \fBdgscat\fP program reads a centralized source graph \fIigfile\fP and
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writes it back on the form of a set of files \fIogfile\fP representing
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fragments of a distributed source graph.
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.PP
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When file names are not specified, data is read from standard input
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and written to standard output. Standard streams can also be
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explicitly represented by a dash '-'.
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.PP
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When the proper libraries have been included at compile time, dgord
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can directly handle compressed graphs, both as input and output. A
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stream is treated as compressed whenever its name is postfixed with
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a compressed file extension, such as in 'brol.grf.bz2' or '-.gz'. The
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compression formats which can be supported are the bzip2 format
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('.bz2'), the gzip format ('.gz'), and the lzma format ('.lzma', on
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input only).
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.PP
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dgord bases on implementations of the MPI interface to spread work
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across the processing elements. It is therefore not likely to be run
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directly, but instead through some launcher command such as \fBmpirun\fP.
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.SH DISTRIBUTED FILE NAMES
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In order to tell whether programs should read from, or write to, a
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single file located on only one processor, or to multiple instances
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of the same file on all of the processors, or else to distinct files
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on each of the processors, a special grammar has been designed,
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which is based on the '%' escape character. Four such escape
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sequences are defined, which are interpreted independently on every
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processor, prior to file opening. By default, when a filename is
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provided, it is assumed that the file is to be opened on only one of
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the processors, called the root processor, which is usually process
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0 of the communicator within which the program is run. The index
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of the root processor can be changed by means of the \fB-r\fP
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option. Using any of the first three escape sequences below will
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instruct programs to open in parallel a file of name equal to the
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interpreted filename, on every processor on which they are run.
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.TP
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.B
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%p
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Replaced by the number of processes in the global communicator in
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which the program is run. Leads to parallel opening.
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.TP
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.B
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%r
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Replaced on each process running the program by the rank of this
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process in the global communicator. Leads to parallel opening.
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.TP
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.B
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%-
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Discarded, but leads to parallel opening. This sequence is mainly
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used to instruct programs to open on every processor a file of
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identical name. The opened files can be, according whether the
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given path leads to a shared directory or to directories that
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are local to each processor, either to the opening of multiple
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instances of the same file, or to the opening of distinct files
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which may each have a different content, respectively (but in
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this latter case it is much recommended to identify files by
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means of the '%r' sequence).
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.TP
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.B
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%%
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Replaced by a single '%' character. File names using this escape
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sequence are not considered for parallel opening, unless one or
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several of the three other escape sequences are also present.
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.RE
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.PP
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For instance, filename 'brol' will lead to the opening of file 'brol'
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on the root processor only, filename '%\fB-brol\fP' (or even 'br%\fB-ol\fP') will
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lead to the parallel opening of files called 'brol' on every
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processor, and filename 'brol%p-%r' will lead to the opening of files
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'brol2-0' and 'brol2-1', respectively, on each of the two processors
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on which the program were to run.
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.SH OPTIONS
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.TP
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.B
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\fB-c\fP
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Check the consistency of the input source graph after
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loading it into memory.
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.TP
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.B
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\fB-h\fP
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Display some help.
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.TP
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.B
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\fB-r\fP\fIpnum\fP
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Set root process for centralized files (default is 0).
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.TP
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.B
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\fB-V\fP
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Display program version and copyright.
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.SH EXAMPLE
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Run \fBdgscat\fP on 5 processing elements to scatter centralized graph
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file brol.grf into 5 gzipped file fragments brol5-0.dgr.gz to
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brol5-4.dgr.gz.
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.PP
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.nf
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.fam C
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$ mpirun -np 5 dgscat brol.grf brol%p-%r.dgr.gz
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.fam T
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.fi
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.SH SEE ALSO
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\fBdgtst\fP(1), \fBdgord\fP(1), \fBgmk_hy\fP(1).
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.PP
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PT-Scotch user's manual.
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.SH AUTHOR
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Francois Pellegrini <francois.pellegrini@labri.fr>
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