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I have solved an optimization problem in CPLEX, but now that I have the optimal solution. I would like to know if there are other optimal solutions. Is is possible to enumerate all other solutions in CPLEX.

Thanks

user2058291
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  • There can be infinitely many optimal solutions. What kind of problem are you working with? If it's a combinatorial optimization problem please add some details. – ayhan Jan 15 '17 at 21:15
  • It is not a complicated problem. It is a Transportaiton Problem with 8 Constraints and 17 Variables! – user2058291 Jan 15 '17 at 22:15
  • Just to add another clarification - you may find that there are infinitely many solutions even for your simple problem. For example, assuming that your transportation problem uses lorries, then you may find that a route requires at least two lorries to carry the goods (e.g. 11 tonnes of goods, and 2 x 10 tonne lorries). But there may be many possible ways to split the goods between those two lorries. In one sense those solutions are equivalent, but the solver would see them as distinct. You are probably more interested in really distinct solutions rather than minor variations. – TimChippingtonDerrick Jan 16 '17 at 16:43
  • Thats a good point I had not thought of that! Thanks – user2058291 Jan 16 '17 at 18:05

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Assuming your model is a MIP, you can make use of the solution pool feature provided in CPLEX: http://www.ibm.com/support/knowledgecenter/SS9UKU_12.5.0/com.ibm.cplex.zos.help/UsrMan/topics/discr_optim/soln_pool/01_soln_pool_title_synopsis.html

Note however that there are limitations, there might be huge or infinite solutions to an optimization problem.

Jon Cardoso-Silva
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