--- name: "dgscat-int32" section: "1" platform: "linux" package: "ptscotch" version: "7.0.7-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/dgscat" --- # dgscat-int32(1) convert distributed source graphs to or from centralized ones Part of [dgscat(1)](/dgscat/1.md). ## NAME **dggath, dgscat, gscat** - convert distributed source graphs to or from centralized ones ## SYNOPSIS ``` dggath [options] [igfile] [ogfile] dgscat [options] [igfile] [ogfile] gscat [options] [igfile] [ogfile] ``` ## DESCRIPTION **The dggath program gathers distributed graphs into centralized** **graphs. It reads a set of files** *igfile* **representing fragments of a** **distributed source graph, and writes them back on the form of a** **single centralized source graph** *ogfile***.** **The dgscat program scatters centralized source graphs into** **distributed graphs. It reads a centralized source graph** *igfile* **and** **writes it back on the form of a set of files** *ogfile* **representing** **fragments of the corresponding distributed source graph.** **The gscat program does exactly the same as dgscat, but does not** **require to be run in a parallel environment. Since gscat processes** **the input centralized graph file as a text stream, it does not need** **to load the full graph in memory before building the distributed** **graph fragment files. It is therefore much less resource consuming,** **but does not allow for the checking of graph consistency, as it has** **no global vision of the graph structure.** **When file names are not specified, data is read from standard input** **and written to standard output. Standard streams can also be** **explicitly represented by a dash '-'.** **When the proper libraries have been included at compile time, dggath** **and dgscat 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').** **dggath and dgscat base 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.** ## DISTRIBUTED FILE NAMES **In order to tell whether programs should read from, or write to, a** **single file located on only one processor, or to multiple instances** **of the same file on all of the processors, or else to distinct files** **on each of the processors, a special grammar has been designed,** **which is based on the '%' escape character. Four such escape** **sequences are defined, which are interpreted independently on every** **processor, prior to file opening. By default, when a filename is** **provided, it is assumed that the file is to be opened on only one of** **the processors, called the root processor, which is usually process** **0 of the communicator within which the program is run. The index** **of the root processor can be changed by means of the -r** **option. Using any of the first three escape sequences below will** **instruct programs to open in parallel a file of name equal to the** **interpreted filename, on every processor on which they are run.** - **%p** **Replaced by the number of processes in the global communicator in** **which the program is run. Leads to parallel opening.** - **%r** **Replaced on each process running the program by the rank of this** **process in the global communicator. Leads to parallel opening.** - **%-** **Discarded, but leads to parallel opening. This sequence is mainly** **used to instruct programs to open on every processor a file of** **identical name. The opened files can be, according whether the** **given path leads to a shared directory or to directories that** **are local to each processor, either to the opening of multiple** **instances of the same file, or to the opening of distinct files** **which may each have a different content, respectively (but in** **this latter case it is much recommended to identify files by** **means of the '%r' sequence).** - **%%** **Replaced by a single '%' character. File names using this escape** **sequence are not considered for parallel opening, unless one or** **several of the three other escape sequences are also present.** **For instance, filename 'brol' will lead to the opening of file 'brol'** **on the root processor only, filename '%-brol' (or even 'br%-ol') will** **lead to the parallel opening of files called 'brol' on every** **processor, and filename 'brol%p-%r' will lead to the opening of files** **’brol2-0' and 'brol2-1', respectively, on each of the two processors** **on which the program were to run.** ## OPTIONS - **-c** **For dggath and dgscat only. Check the consistency of the** **input source graph after loading it into memory.** - **-h** **Display some help.** - **-inbr** **For gscat only. Create an imbalanced distributed graph,** **in which the distributed graph files for all processes** **will receive extit{nbr} vertices of the graph, save** **for the file for the last process, which will receive** **all the remaining vertices.** - **-r*pnum*** **Set root process for centralized files (default is 0).** - **-V** **Display program version and copyright.** ## EXAMPLE **Run dgscat on 5 processing elements to scatter centralized graph** **file brol.grf into 5 gzipped file fragments brol5-0.dgr.gz to** **brol5-4.dgr.gz.** ``` $ mpirun -np 5 dgscat brol.grf brol%p-%r.dgr.gz ``` ## SEE ALSO **[dgmap(1)](/dgmap/1.md), [dgord(1)](/dgord/1.md), [dgtst(1)](/dgtst/1.md), [gmk\_hy(1)](/gmk_hy/1.md).** **PT-Scotch user's manual.** ## AUTHOR **Francois Pellegrini \**