I'm implementing the Grötschel-Holland algorithm for solving the matching problem using linear programming. The key of this algorithm is that its use a few restriction of the matching polyhedron and, if the solution hasn't integer coordinates, find a good cut-plane and optimize again. I'm working in Python.
My question is: If I create a model "m",I optimize it using m.optimize() and I add some constrains using m.addConstr, when I optimize again Gurobi use again the pre-solve or it use some information of the previous optimization process.
I'm a little surprised because I'm doing a time-computation analysis versus the integer programming method with Gurobi and I'm getting: for less than 1000 edges, GH is better, and for more the integer solver is better.
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