Search found 11 matches

by hossein60
4 months ago
Forum: Solvers
Topic: Different results with zero optimality gap: MIP against SOS2
Replies: 2
Views: 524

Re: Different results with zero optimality gap: MIP against SOS2

Many thanks for your attention. The original problem is non-convex with many local solutions. However, with a piecewise linearization technique, the approximate equivalent MILP model is built which is convex in the relaxed form (relaxing integer values). Consequently, it is expected that all MILP so...
by hossein60
4 months ago
Forum: Solvers
Topic: Different results with zero optimality gap: MIP against SOS2
Replies: 2
Views: 524

Different results with zero optimality gap: MIP against SOS2

Different results with zero optimality gap: MIP against SOS2 Dear all I have a MIP model with some SOS2 constraints. I implement the SOS2 constraints with two approaches including SOS2 variable definition in GAMS, i.e. native SOS2 provided by CPLEX, and a MIP technique enforcing SOS2 constraints usi...
by hossein60
8 months ago
Forum: Modeling
Topic: How to implement integration in objective function of a model
Replies: 0
Views: 709

How to implement integration in objective function of a model

Dear all I am trying to minimize area between two curves using numerical integration by trapezoidal rule. The integral bounds are also variables in my model, i.e. int(f(x),[a , b]) wherein a and b are variables representing integral bounds. Any idea for formulation of the model is appreciated. Thank...
by hossein60
8 months ago
Forum: Solvers
Topic: Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?
Replies: 2
Views: 659

Re: Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?

Hi, Thank you once again. But I could not implement the method. Certainly my CPLEX does not include miptrace maybe because of using older version of GAMS, i.e. 24.1. The provided file in following link also did not helped. Advanced Use of GAMS Solver Links: https://old.gams.com/presentations/present...
by hossein60
8 months ago
Forum: Modeling
Topic: Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?
Replies: 2
Views: 379

Re: Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?

Hi,

Thanks. But I can not find it in doc/solver/CPLEX maybe because of using GAMS 24.1.

Best regards;
Hossein
by hossein60
8 months ago
Forum: Solvers
Topic: Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?
Replies: 2
Views: 659

Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?

Dear all

I want to record some outputs generated by CPLEX such as the iteration number, objective and the associated time so that I can plot some convergence characteristic, for example objective-iteration number, objective-time and objective-number of nodes.
Have you any idea?

Best regards;
Hossein
by hossein60
8 months ago
Forum: Modeling
Topic: Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?
Replies: 2
Views: 379

Saving some iteration log data generated by CPLEX, as a MIP solver, into parameters. Is this possible?

Dear all I want to record some outputs generated by CPLEX such as the iteration number, objective and the associated time so that I can plot some convergence characteristic, for example objective-iteration number, objective-time and objective-number of nodes. Have you any idea? Best regards; Hossein
by hossein60
8 months ago
Forum: Modeling
Topic: Increasing ‘reslim’ but weaker result in a mip solver
Replies: 5
Views: 590

Re: Increasing ‘reslim’ but weaker result in a mip solver

Dear Fred

Many thanks for taking the time and effort in answering this post.

Best regards;
Hossein
by hossein60
8 months ago
Forum: Modeling
Topic: Increasing ‘reslim’ but weaker result in a mip solver
Replies: 5
Views: 590

Re: Increasing ‘reslim’ but weaker result in a mip solver

Many thanks for your quick answer. The model is minimizing problem. I didn’t mean that the solutions with reslim=300 always are better than ones with reslim=600. Actually, the obtained results usually oscillate between two or three objective values for the both reslims. I did my best to keep everyth...
by hossein60
8 months ago
Forum: Modeling
Topic: Increasing ‘reslim’ but weaker result in a mip solver
Replies: 5
Views: 590

Increasing ‘reslim’ but weaker result in a mip solver

Dear all I am solving a MILP model using CPLEX as a solver. I increase the ‘reslim’ to enhance the solution and reduce the optimality gap. But sometimes increasing the ‘reslim’ leads to worse objective. Initially I guessed that probably it is because of different CPU and/or RAM amount engaged by ope...