GRF Files, Type 1

These are some examples of GRF files of type 1.

GRF files are used to store an abstract graph, and in some cases, an embedding of the graph, that is, a description of how to place the nodes in the unit square so that the graph can be drawn.

The type 1 version of GRF files does NOT include embedding information.

The original format derives from the SPREMB package developed at the University of Queensland, Australia.

We assume that the nodes of the graph are numbered, with a typical node numbered I. Information about node I is stored on the I-th line of the file. (It is not actually necessary that the I-th node be listed on the I-th noncomment line, but it is customary.) Edges of the graph that begin at node I will be described by listing the nodes at the terminal end of the edge. Thus, if there are edges from node I to nodes J(1), J(2), ..., J(K), then these nodes will be listed.

The I-th line of the file is

        I  J(1) J(2) ... J(K)
      

Related Data and Programs

GRF_IO, a FORTRAN90 library which reads or writes a GRF file;

GRF_TO_EPS, a FORTRAN90 program which converts a GRF file to EPS format;

Reference:

1. Peter Eades, Ian Fogg, David Kelly,
   SPREMB: A System for Developing Graph Algorithms,
   Congressus Numerantium,
   Volume 66, December 1988, pages 123-140.
2. Stephen Skiena,
   Implementing Discrete Mathematics: Combinatorics and Graph Theory with Mathematica,
   Addison Wesley, 1990,
   ISBN: 0201509431,
   LC: QA164.S56.

Sample files

• coxeter.grf, the Coxeter graph, 28 nodes and 84 edges;

You can go up one level to the DATA page.