# Is there a bug with using chromatic_number together with Gurobi? [closed]

I have installed the LP solver Gurobi, and it seems to work successfully work with the vertex_coloring() command. But I wanted to compare runtimes with chromatic_number, and Sage seems to hang whenever I try this.

I construct a graph G, and then when I run the command G.chromatic_number(algorithm="MILP"), Sage hangs. I can tell something has gone wrong because it doesn't come back even when I give it a very small simple graph G, and because Linux tells me that I know have a zombie process.

Any suggestions would be much appreciated.

to reproduce this, it would be good to know precisely on what G it hangs, and also your Gurobi and Sage versions...