Search found 7 matches

by moosavi_69
6 hours ago
Forum: Modeling
Topic: Why does GAMS change binary variables to positive ones in a loop?
Replies: 0
Views: 8

Why does GAMS change binary variables to positive ones in a loop?

Dear friends, I have coded a scheduling problem in GAMS using the Sample Average Approximation. This model is a MILP mathematical model. I have chosen Cplex as the solver for this problem. The code solves a problem in a loop for multiple times, and it fixes binary variables, i.e., xa, and xaa, in ea...
by moosavi_69
1 week ago
Forum: Syntax
Topic: How can I report and store the optimality status of solutions in the GAMS (in gdx files)?
Replies: 1
Views: 51

Re: How can I report and store the optimality status of solutions in the GAMS (in gdx files)?

I found the answer to this question. After solving a model, it saves its features in its attributes. For further details, interested readers can see the following link: https://www.gams.com/latest/docs/UG_ModelSolve.html#UG_ModelSolve_ModelAttributes For instance, if we want to optimize a model enti...
by moosavi_69
1 week ago
Forum: Syntax
Topic: How can I report and store the optimality status of solutions in the GAMS (in gdx files)?
Replies: 1
Views: 51

How can I report and store the optimality status of solutions in the GAMS (in gdx files)?

Dear sir/ madam, I have coded a problem and used Cplex as the solver. I want to store the optimality status of solutions of this problem. To be more precise, I want to store them in gdx files. Although the GAMS indicates this issue on its report page (i.e., Absolute Gap), I could not find a way to r...
by moosavi_69
4 months ago
Forum: Solvers
Topic: CPU time for large-scale instances
Replies: 2
Views: 365

Re: CPU time for large-scale instances

Dear Steve, I am grateful for your prompt attention. Following to your question regarding the decision variables, I have to tell you that variables in this problem are positive integer or binary. To be more precise, around 15,000 of them are binary variables and 8,000 of them are positive integer va...
by moosavi_69
4 months ago
Forum: Solvers
Topic: CPU time for large-scale instances
Replies: 2
Views: 365

CPU time for large-scale instances

Dear friends, I have a question. Note that this inquiry is a question asked by a reviewer and I have to fully address his concern. His concern: " The model is really complex with thousands of constraints. I have difficulty in imaging that the exact method needs few seconds... " Let me explain the pr...
by moosavi_69
9 months ago
Forum: Syntax
Topic: Unknown option (mipstart=1)
Replies: 2
Views: 496

Re: Unknown option (mipstart=1)

Hi, mipstart is not a GAMS but a solver option, see e.g. the CPLEX solver manual: https://www.gams.com/latest/docs/solvers/cplex/index.html#CPLEXmipstart Hence, mipstart needs to be set in a solver option file: https://www.gams.com/latest/docs/solvers/introduction/index.html#BASIC_USAGE_SOLVER_OPTI...
by moosavi_69
9 months ago
Forum: Syntax
Topic: Unknown option (mipstart=1)
Replies: 2
Views: 496

Unknown option (mipstart=1)

Hey guys, I have a problem with GAMS and want you to help me (PLS). I have developed a two step algorithm, in which a heuristic algorithm creates a relatively high quality and feasible solution at the first step, then a MIP-based algorithm (or partial MIP algorithm) improves the solution found at th...