I have a MILP problem. I use CBC solver to solve it. If I call CBC through GAMS, the computation time will be short. But when I solve it directly using CBC.exe, it takes too much time. In both cases, I use the default value of the parameters. Is it GAMS that optimizes the parameters of CBC? Thank you to tell me the reason.
GAMS does not optimize the solver parameters explicitly. Though, in some cases it might set its own defaults. Also, is it possible, that your two formulations of the model are a little different?