Hi I got an MIP model which I am trying to solve it by CPLEX. I don’t know why there is a gap between the “MIP Solution” and “Final solve” value. Is there anyway that I can keep the MIP solution instead of Final solve?

Thanks,

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Dear Omid,

If a MIP has continuous variables, the objective of the fixed model can differ from objective value reported when the incumbent solution was first found. This can happen because CPLEX has many different procedures to derive integer feasible solutions. Some of them provide an optimal basis to a node LP that will also be optimal for the fixed problem, but others do not. In the latter case, changes to the continuous variables in the fixed model may yield an improvement in the objective and this is what is happening with the model. This behavior will disappear, if you set optca/optcr to Zero.

See the following reference: http://www-01.ibm.com/support/docview.wss?uid=swg21399941

On Thu, Jun 4, 2015 at 5:31 PM, omid ziaee wrote:

Hi I got an MIP model which I am trying to solve it by CPLEX. I don’t know why there is a gap between the “MIP Solution” and “Final solve” value. Is there anyway that I can keep the MIP solution instead of Final solve?

Thanks,

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Hi,

This sometimes happens with numerically unstable models. You can a) try to use “numericalemphasis 1” and/or “scaind 1” or manually work on the model numerics b) skip the final solve via “solvefinal 0”. This this case you will only get a primal solution (not duals .m).

Hope this helps,

Michael Bussieck - GAMSWorld Coordinator

On Friday, June 5, 2015 at 2:26:48 AM UTC-4, omid ziaee wrote:

Hi I got an MIP model which I am trying to solve it by CPLEX. I don’t know why there is a gap between the “MIP Solution” and “Final solve” value. Is there anyway that I can keep the MIP solution instead of Final solve?

Thanks,

–

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Reply-to: gamsworld@googlegroups.com

Thank you for your respond. I don’t know how to keep the best answer instead of final solution. The answer shown in .lst file is final solution. I want to get the best answer. How can I get that answer?

Omid,

On Friday, June 5, 2015 at 1:46:39 AM UTC-5, Michael Bussieck wrote:

Hi,

This sometimes happens with numerically unstable models. You can a) try to use “numericalemphasis 1” and/or “scaind 1” or manually work on the model numerics b) skip the final solve via “solvefinal 0”. This this case you will only get a primal solution (not duals .m).

Hope this helps,

Michael Bussieck - GAMSWorld Coordinator

On Friday, June 5, 2015 at 2:26:48 AM UTC-4, omid ziaee wrote:

Hi I got an MIP model which I am trying to solve it by CPLEX. I don’t know why there is a gap between the “MIP Solution” and “Final solve” value. Is there anyway that I can keep the MIP solution instead of Final solve?

Thanks,

–

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Dear Masoud,

I have changed both optrc and optca to zero but I got the same result. I was wondering if there is anyway that I keeps the MIP solution instead of Final solve in .lst file.

Thanks,

On Friday, June 5, 2015 at 7:55:38 AM UTC-5, masoud barati wrote:

Dear Omid,

If a MIP has continuous variables, the objective of the fixed model can differ from objective value reported when the incumbent solution was first found. This can happen because CPLEX has many different procedures to derive integer feasible solutions. Some of them provide an optimal basis to a node LP that will also be optimal for the fixed problem, but others do not. In the latter case, changes to the continuous variables in the fixed model may yield an improvement in the objective and this is what is happening with the model. This behavior will disappear, if you set optca/optcr to Zero.

See the following reference: http://www-01.ibm.com/support/docview.wss?uid=swg21399941

On Thu, Jun 4, 2015 at 5:31 PM, omid ziaee wrote:

Hi I got an MIP model which I am trying to solve it by CPLEX. I don’t know why there is a gap between the “MIP Solution” and “Final solve” value. Is there anyway that I can keep the MIP solution instead of Final solve?

Thanks,

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Reply-to: gamsworld@googlegroups.com

Could you please guide me about solution pool if you have any information?

On Friday, June 5, 2015 at 1:46:39 AM UTC-5, Michael Bussieck wrote:

Hi,

This sometimes happens with numerically unstable models. You can a) try to use “numericalemphasis 1” and/or “scaind 1” or manually work on the model numerics b) skip the final solve via “solvefinal 0”. This this case you will only get a primal solution (not duals .m).

Hope this helps,

Michael Bussieck - GAMSWorld Coordinator

On Friday, June 5, 2015 at 2:26:48 AM UTC-4, omid ziaee wrote:

Hi I got an MIP model which I am trying to solve it by CPLEX. I don’t know why there is a gap between the “MIP Solution” and “Final solve” value. Is there anyway that I can keep the MIP solution instead of Final solve?

Thanks,

–

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For more options, visit https://groups.google.com/d/optout.