Short manual of Compute-cfn
---------------------------

Author: Jan Goedgebeur (jan.goedgebeur@ugent.be)
In collaboration with Davide Mattiolo and Giuseppe Mazzuoccolo

Compute-cfn computes the circular flow number of a (bridgeless) cubic graph. The circular flow number of a graph G is the least real number r such that G admits a circular nowhere-zero r-flow.

This program has been tested on Linux and Mac OS X.


Installation
------------

The latest version of Compute-cfn can be obtained from http://caagt.ugent.be/cfn/

- Compile Compute-cfn using the command "make".

(Alternatively, compile using the command: gcc -O4 -mpopcnt compute-cfn.c -o compute-cfn)


Usage
-----
An overview of all options can also be found by executing "./compute-cfn -h".


Usage: ./compute-cfn <r-value> [options]
At least the desired circular flow number <r-value> must be specified.

Valid options are:
  all: Only output graphs with cfn equal to r-value (instead of the default which outputs those with cfn >= r-value).
  mod <rest> <modulo>: splits the inputgraphs in <modulo> parts. Here part <rest> will be executed.
  modbisect <rest> <modulo>: splits the computation for one specific inputgraph in <modulo> parts. Here part <rest> will be executed. Only works in computation with option 'all'.

Remark: the inputgraphs are read from stdin in multicode format (see Appendix A) and the graphs with the desired circular flow number are written to stdout in the same format.

Don't hesitate to contact us at jan.goedgebeur[at]ugent.be if you have any further questions or suggestions.


Changelog
---------

2019-09-17: First release.


Appendix A: definition of the multicode format
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This code is binary. The first entry is the number of vertices.
Vertices are numbered 1,...,n. For each vertex x there is a list of
neighbours with higher labels than x, followed by a zero.
The last list is always empty (there are no neighbours of n with a higher number than n),
therefore the last "list" is not followed by a zero.
After the last byte the next graph follows.

The codelength of a graph in multicode is number of vertices + number of edges.

More information about this format + a program to translate multicode to adjacency lists can be found at: http://hog.grinvin.org/Formats.action#multicode