Name  graphcoloring_decision.gringo 

Class Tree  
Submitter  Martin Gebser 
Author  Martin Gebser and Roland Kaminski 
Description 
Description =========== A graph is a set of nodes and a symmetric, binary link relation on nodes. Given a set of N colours, a graph is colourable if each node can be assigned a colour in such a way that any two nodes that are linked together. Input  A number of node facts which give the names of the nodes. Node names are consecutive, ascending integers starting from 1. A number of colour facts which give the names of the colours. Colour names start with the sequence "red", "green", "blue". A number of link facts which say which nodes are linked. Note that if link(N1,N2). is included then so will link(N2,N1). For example: node(1). node(2). node(3). link(1,2). link(2,1). link(2,3). link(3,2). link(3,1). link(1,3). colour(red). colour(green). colour(blue). Output  The initial facts and a set of choosenColour predicates, one for each node, specifying the node's colour. Continuing the example: chosenColour(1,red). chosenColour(2,green). chosenColour(3,blue). Calibration  The Two Possible Values of the Chromatic Number of a Random Graph (with A. Naor) Annals of Mathematics, 162 (3), (2005), 13331349. http://www.cs.ucsc.edu/~optas/papers/kcol.pdf Suggests that given a random graph with n nodes and a density of (d/n) then the chromatic number is either k or k+1 where k is the smallest number such that d < 2k log(k). Thus settings with around 125150 nodes (135 is good), link density of 0.1 (d = 1215) and 5 colours gives difficult programs. Author: Martin Brain 
Created  20090327 12:58 
Modified  20090327 12:58 
Languages  
Language Features  
Compatible Instance Classes  
Input Predicates 

Output Predicates 

Encoding Parameter 

Standalone  No 


Attributes  
Content 