Why the gap is so big?

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  • Silke Horn

    The huge gap means that the objective of the root relaxation (i.e., the optimal fractional solution) is far away from the best integer solution that has been found so far.

    In your log, I can see that Gurobi moves the bound quite a bit, from -4337.444e at the end of the root relaxation to -601.04029 when you interrupted the solve, while the incumbent solution is barely moving.

    You could experiment with different values of the MIPFocus parameter or more aggressive cuts to make the bound move faster, but if you could improve the model by tightening the LP relaxation (i.e., change your constraints or add new ones so that the optimal solution of the root relaxation gets closer to the optimal integer solution), that would probably help a lot more.

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