Originally posted by: SystemAdmin
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> 1.what's the relation between the actual compute time in c++ and the total compute time displayed in cmd?
Sorry, I don't understand this question (specifically the "displayed in cmd"). Are you asking about the difference between the solution time reported by CPLEX's C++ API and "wall clock" time? Or the difference between the C++ API and solving the same problem in the interactive optimizer?
> 2.In order to decrease the compute time, how did I choose the method between big-m and if-then, what's their corresponding circumstances？ They are in a great distance when solving particular problem.
My understanding (not guaranteed to be accurate) is that CPLEX handles indicator ("if-then") constraints by one of two methods (determined by its internal logic): convert them into branching rules; or convert them into "big-M" constraints. My feeling is that more often it chooses the latter. So the main difference between your implementing a constraint using "big-M" and your implementing it as "if-then" would be whether you can find a valid choice for M that is smaller than what CPLEX would deduce.
Paul
Mathematicians are like Frenchmen: whenever you say something to them, they translate it into their own language, and at once it is something entirely different. (Goethe)
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