current bounds on the number of colors: 0 -- 6 Gurobi 5.0.1 (linux64) logging started Sat Dec 15 16:12:38 2012 Optimize a model with 6 rows, 18 columns and 18 nonzeros Presolve removed 6 rows and 18 columns Presolve time: 0.00s Explored 0 nodes (0 simplex iterations) in 0.00 seconds Thread count was 1 (of 16 available processors) Optimal solution found (tolerance 1.00e-04) Best objective 0.000000000000e+00, best bound 0.000000000000e+00, gap 0.0% current bounds on the number of colors: 0 -- 3 Gurobi 5.0.1 (linux64) logging started Sat Dec 15 16:12:38 2012 Optimize a model with 6 rows, 6 columns and 6 nonzeros Presolve removed 6 rows and 6 columns Presolve time: 0.00s Explored 0 nodes (0 simplex iterations) in 0.00 seconds Thread count was 1 (of 16 available processors) Optimal solution found (tolerance 1.00e-04) Best objective 0.000000000000e+00, best bound 0.000000000000e+00, gap 0.0% optimal solution found: number of colors: 1