I have an MIP problem solved with glpk. However the result shows only suboptimal because I can manully find a solution have better result. I see something in output I didn't understand:
when I run glpsol with --wfreemap, glpsol solves problem and give the problem in free mps format. The glpsol says "(LP) optimal solution found and integer optimal solution found" (senario 1). However, when I run glpsol using the generated mps file (senario 2), it says:
PROBLEM HAS NO DUAL FEASIBLE SOLUTION lpx_integer: optimal solution of LP relaxation required
So, do these 2 senarios differ? why? How do I improve to get optimal MIP solution?
(side note: when I run this mps with lp_solve, it also say This problem is unbounded which seems agree with senario 2).
Thanks in advance.
Andy
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