GRF_IO
GRF files
Read and Write Utilities

GRF_IO is a FORTRAN90 library which reads or writes a GRF file containing information about an abstract graph.

The file includes information about

• adjacency, that is, which nodes are connected to a given node;
• embedding, that is, how to place each node in the unit square so that a drawing of the graph is visually pleasing and "readable".

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Related Data and Programs:

FLOYD is a FORTRAN90 library which implements Floyd's algorithm for finding the shortest distance between pairs of nodes on a directed graph.

GRAFFITI is a dataset directory which contains 195 abstract graphs, with adjacency and embedding information, stored in the GRF format.

GRF is a data directory which contains a description of the GRF format and some examples.

GRF_DISPLAY, a MATLAB program which reads a GRF file defining a mathematical graph and displays it in the MATLAB graphics window.

GRF_DISPLAY_OPEN_GL, a C++ program which reads a GRF file defining a mathematical graph and displays it in an OpenGL graphics window.

GRF_IO is available in a C++ version and a FORTRAN90 version and a MATLAB version.

GRF_TO_EPS is a FORTRAN90 program which can make an encapsulated PostScript image of a GRF file.

GRF_TO_XYL, a FORTRAN90 program which converts information describing the adjacency and embedding of an abstract graph from GRF to XYL format.

XGED is a C program which is an X-Window based editor for GRF files.

Reference:

1. Peter Eades, Ian Fogg, David Kelly,
   SPREMB: A System for Developing Graph Algorithms,
   Congressus Numerantium,
   Volume 66, December 1988.
2. Stephen Skiena,
   Implementing Discrete Mathematics: Combinatorics and Graph Theory in Mathematica,
   Addison Wesley, 1990.
3. http://www.combinatorica.com/
   the COMBINATORICA web page.

• grf_io.f90, the source code.
• grf_io.csh, commands to compile the source code.

Examples and Tests:

• grf_io_prb.f90, a sample calling program.
• grf_io_prb.csh, commands to compile, link and run the sample calling program.
• grf_io_prb_output.txt, the output file.
• coxeter.grf, a GRF file created by one test and read by another.

List of Routines:

• CH_CAP capitalizes a single character.
• CH_EQI is a case insensitive comparison of two characters for equality.
• CH_TO_DIGIT returns the integer ( kind = 4 ) value of a base 10 digit.
• DIGIT_TO_CH returns the character representation of a decimal digit.
• GET_UNIT returns a free FORTRAN unit number.
• GRF_DATA_PRINT prints the data of a GRF file.
• GRF_DATA_READ reads the data of a GRF file.
• GRF_DATA_WRITE prints the data to a GRF file.
• GRF_EXAMPLE sets up a GRF example.
• GRF_EXAMPLE_SIZE sizes a GRF example.
• GRF_HEADER_PRINT prints the header of a GRF file.
• GRF_HEADER_READ reads the header of a GRF file.
• GRF_HEADER_WRITE writes the header of a GRF file.
• GRF_WRITE writes a GRF file.
• S_TO_I4 reads an integer value from a string.
• S_TO_R8 reads an R8 value from a string.
• TIMESTAMP prints the current YMDHMS date as a time stamp.

You can go up one level to the FORTRAN90 source codes.