---
name: "dgord"
section: "1"
platform: "linux"
package: "scotch"
version: "7.0.17-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/dgord"
---

# dgord(1)

compute sparse matrix orderings of graphs in parallel

## NAME

**dgord** - compute sparse matrix orderings of graphs in parallel

## SYNOPSIS

```
dgord [options] [gfile] [ofile] [lfile]
```

## DESCRIPTION

**The dgord program computes, in a parallel way, an ordering of a** **Scotch source graph representing the pattern of some symmetric** **sparse matrix.**

**Source graph file** *gfile* **is either a centralized graph file, or a set** **of files representing fragments of a distributed graph. The resulting** **ordering is stored in file** *ofile***. 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, dgord** **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').**

**dgord bases 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.**

## OPTIONS

- **-copt**

  **Choose default ordering 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.**

  - **x**

    **enforce scalability.**

- **-h**

  **Display some help.**

- **-m*mfile***

  **Save column block mapping data to file** *mfile***. Mapping** **data specifies, for each vertex, the index of the column** **block to which this vertex belongs.**

- **-o*strat***

  **Use parallel graph ordering strategy** *strat* **(see** **PT-Scotch user's manual for more information).**

- **-r*pnum***

  **Set root process for centralized files (default is 0).**

- **-t*tfile***

  **Save partitioning tree data to file** *tfile***. Partitioning** **tree data specifies, for each vertex, the index of the** **first vertex of the parent block of the block to which** **the vertex belongs. Altogether with the mapping data** **provided in file** *mfile***, it allows one to rebuild the** **separator tree of the nested dissection process.**

- **-V**

  **Display program version and copyright.**

- **-v*verb***

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

  - **s**

    **strategy information.**

  - **t**

    **timing information.**

## EXAMPLES

**Run dgord on 5 processing elements to reorder matrix graph brol.grf** **and save the resulting ordering to file brol.ord, using the default** **sequential graph ordering strategy:**

```
    $ mpirun -np 5 dgord brol.grf brol.ord
```

**Run dgord on 5 processing elements to reorder the distributed matrix** **stored on graph fragment files brol5-0.dgr to brol5-4.dgr, and save** **the resulting ordering to file brol.ord (see [dgscat(1)](/dgscat/1.md) for an** **explanation of the '%p' and '%r' sequences in names of distributed** **graph fragments).**

```
    $ mpirun -np 5 dgord brol%p-%r.dgr brol.ord
```

## SEE ALSO

**[dgtst(1)](/dgtst/1.md), [dgscat(1)](/dgscat/1.md), [gmk\_hy(1)](/gmk_hy/1.md), [gord(1)](/gord/1.md).**

**PT-Scotch user's manual.**

## AUTHOR

**Francois Pellegrini \<francois.pellegrini@labri.fr\>**