# Questions tagged [gams]

For questions related to GAMS (General Algebraic Modeling System), a high-level modeling system for mathematical optimization.

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### Ordering a set in GAMS

I'm trying to solve a problem very similar to this one, where I'm trying to find an optimal order. How would I actually plug this into GAMS? It gives out a single value rather than an ordering. I ...
96 views

### Building model takes so much time in Cplex

I am a beginner in CPLEX. I have a model with about 1 million constants and 800k rows and 1.6 million columns. I implemented in both GAMS and CPLEX (C# as the platform). The final solution for both is ...
110 views

### Any good resource for solving power system optimization in GAMS?

I am looking for some resources to learn the modelling tricks of GAMS in power system optimisation problems.
107 views

### GAMS summing over subset

I am trying to sum over a subset between $t+1$ and $t+U-1$ as follows $$y_i^t+\sum_{k=t+1}^{t+Ut_i-1}z_i^k\le1$$ but I could not define the condition within sum. ...
102 views

### GAMS: Is there a way to retrieve the gap from the final solve statement

Good evening, I am looking for a way to retrieve information from the final solve statement. Lower bound and Gap would be nice. I am working with the python api but i can only get the final obj. value ...
242 views

### GAMS default Solver doesn't use much of my RAM and CPU

I noticed that when I run the solver via the GAMS IDE or Python API I don't use more than ~33% of my RAM. Is there an artificial barrier which I can put up or disable?
217 views

### CPLEX output log

Whats the difference between MIP solution and Final Solve? I am trying to benchmark some solution approaches and I am not sure which of those is the more significant... sometimes they have the same ...
104 views

### GAMS CPLEX solver solves big problem instances suspiciously fast

I am having trouble with my Problem Instances, which seem to be not "complicated" enough.. Is there a way to find out what the problem is? It is being solved in a matter of seconds even if ...
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### Issue interpreting sets of constraints in AMPL

I'm new to AMPL and am trying to model the following constraints. \begin{align}y_{ij3}&\le\sum_\ell X_{j\ell2}\quad(m=2,k=3)\\y_{ijk}&\le\sum_\ell\sum_mx_{j\ell m},\quad\forall i\in I,\forall ...