Hello everyone,

I’m modelling a MIP. The solver is oriented to minimise the objective function. I know that the best solution of the MIP is 43,8 (I’ve solved it by hands). When I ran GAMS, the solver (CPLEX) did not reach the best value, as you guys can see:

Solution satisfies tolerances.

MIP Solution: 47.400000 (277 iterations, 24 nodes)

Final Solve: 47.400000 (18 iterations)

Best possible: 43.800000

Absolute gap: 3.600000

Relative gap: 0.075949

Then, based on a tip I’ve gotten here (thank you Fred), I set optcr = 0 (I also set other values). As a result, the solution changed, but it wasn’t the best one (43,8) yet, as shown below:

Proven optimal solution.

MIP Solution: 44.200000 (289 iterations, 27 nodes)

Final Solve: 44.200000 (15 iterations)

Best possible: 44.200000

Absolute gap: 0.000000

Relative gap: 0.000000

I’ve tried all the MIP solvers that a demo license provide. None of them have reached the best solution. Besides that, I’ve tried starting points, which didn’t change the result at all.

Could anyone here suggest a way to fix it?

thank you guys in advance

cheers!