ASKSAGE: Sage Q&A Forum - Latest question feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Sun, 04 Jan 2015 14:35:41 -0600optimizing graph coloring for small chromatic numberhttps://ask.sagemath.org/question/25395/optimizing-graph-coloring-for-small-chromatic-number/I am using Sage to compute chromatic number of some moderately large graphs G (a few thousand vertices). These graphs are relatively sparse (average degree < 15) and the chromatic number is fairly small–––the graphs I've been looking at tend to have chromatic number either 4 or 5. For my purposes, though, there is a big difference between 4 and 5.
––I've been using G.chromatic_number() as a black box, but is there some way I could just ask Sage directly if the graph is 4-colorable? (If the answer is 'no' maybe I don't care about whether the chromatic number is actually 5, 6, or larger.)
––Also, is there anything else I can do to optimize chromatic number calculations in Sage if I know a priori that the chromatic number is relatively small?
MattKahleSun, 04 Jan 2015 14:35:41 -0600https://ask.sagemath.org/question/25395/code for tail and head of an edge in a bipartite graphhttps://ask.sagemath.org/question/10050/code-for-tail-and-head-of-an-edge-in-a-bipartite-graph/how to write a code for finding tail and head of an edge in a bipartite graph?REKHA BISWALMon, 22 Apr 2013 01:05:23 -0500https://ask.sagemath.org/question/10050/