Last revision: May 08, 1993
Abbreviated: Bart Massey March 02, 2001
An input file contains all the information about a graph needed to define a coloring problem.
In this format, nodes are numbered from 1 up to n edges in the graph.
Files are assumed to be well-formed and internally consistent: node identifier values are valid, nodes are defined uniquely, exactly m edges are defined, and so forth.
c This is an example of a comment line.
p FORMAT NODES EDGESThe lower-case character p signifies that this is the problem line. The FORMAT field is for consistency with the previous Challenge, and should contain the word ``edge''. The NODES field contains an integer value specifying n, the number of nodes in the graph. The EDGES field contains an integer value specifying m, the number of edges in the graph.
e W VThe lower-case character e signifies that this is an edge descriptor line. For an edge (w,v) the fields W and V specify its endpoints.
s TYPE SOLUTIONThe lower-case character s signifies that this is a solution line. The TYPE field denotes the type of solution contained in the file. This should be the string ``col'' denoting a graph coloring.
The SOLUTION field contains an integer corresponding to the solution value. This is the number of colors used for graph coloring.
The lower-case character b signifies that this is a bound on the the solution. The BOUND field contains an integer value that gives a bound on the solution value. This bound is a lower bound on the number of colors needed for coloring the graph.
l V N
The lower-case character l signifies that this is a label line, used for graph coloring. The V field gives the node number for the node in the clique while the N field gives the corresponding label. There will be one label line for each node in the graph.
c FILE: myciel3.col
c SOURCE: Michael Trick (email@example.com)
c DESCRIPTION: Graph based on Mycielski transformation.
c Triangle free (clique number 2) but increasing
c coloring number
p edge 11 20
e 1 2
e 1 4
e 1 7
e 1 9
e 2 3
e 2 6
e 2 8
e 3 5
e 3 7
e 3 10
e 4 5
e 4 6
e 4 10
e 5 8
e 5 9
e 6 11
e 7 11
e 8 11
e 9 11
e 10 11