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 ...
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96
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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 ...
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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.
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107
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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.
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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 ...
- 533
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242
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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?
- 533
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2
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217
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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 ...
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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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How can one iterate over all instances and solve them in GAMS?
I wrote my model down in GAMS:
all sets
parameter
obj. function
constraints
and used $include in order to feed the model differently sized data...
I am currently using
...
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GAMS export to excel in a loop
I am looking for a way to write data from several iterations during a loop process into my excel.
How can i change the location it is written to during every loop iteration?
those 2 lines would keep ...
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Looking for an example of a heuristic implementation in GAMS
I am new to GAMS and the documentation is not helping me to make fast progress.
I am looking for an example implementation similar to Relax and Fix heuristic
where in several iterations subsets of ...
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How to automatize instance generation for GAMS?
Gams problem instances can be saved in a .inc file what is basically just a .txt file and u can make gams read from that, but how can i automatize the generation process for those problem instances? I ...
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How to build a GAMS model in python
I looked at the GAMS python API but the documentation only describing already predefined models (run .gms with some tweaking options).
My question is now: Can I somehow build a gams model from scratch ...
- 533
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How to set solver options in Pyomo with GAMS Python API?
Did anyone have experiences with Pyomo and GAMS as solver? I had looked into the pyomo documentation (GAMSShell Solver) and in the CPLEX Manuals, but doesnt find the correct syntax.
My Code looks like:...
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Quantifying Feasibility
I have a scheduling model formulation ( experimental setup) that takes in product states as input (sample points) and checks the model status (response) and returns feasible or infeasible.
My plan is ...
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2
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534
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GAMS Sum over a subset
I have the following sets, variables, and parameters in a GAMS model.
set \quad h/1*3/;
alias (h,t);
Positive variables are $p_d(h)$, $p_c(h)$ and $e(h)$. ...
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Are Python and Julia used for optimization in industry?
I am giving a small computer exercise that aims at teaching students the basics of a modelling language to model small optimization problems. So far I have been using the modelling language GAMS as ...
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Modeling and solvers
I have just started to dive into OR world on my work. Currently we are using GAMS with Gurobi but some of us have strong programming background and would like to have more programmatic approach to OR. ...
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Tolerance for equality in GAMS/CPLEX
Is there an option in GAMS that sets the tolerance for declaring two real numbers to equal?
For example, how can I tell GAMS or GAMS/CPLEX that $0.999100 = 0.99909$?
Thank you for your help!
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How can I do this in GAMS?
I am mimicking a GAMS model that was introduced in Soler et al. (2013)1 to compare my new model with its results.
In a nutshell, assume we have a variable $t$ that is supposed to only take certain ...
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Is this formulation linear or non-linear?
Can you help me figure out if this formulation constitutes a non-linear problem? I believe It is a linear problem but my solver (GAMS) is unable to produce a acceptable solution.
$x,y$ and $\text{...
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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 ...
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Get a MPS file using NEOS/GAMS web interface
I'm trying to use Neos/GAMS to solve an optimization problem. I will need to get a MPS file from the model. With using GAMS IDE it is easy to use an option file to get it but, it needs a licence file ...
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Comparison of Algebraic modelling languages and general programming languages
Some optimization software/frameworks (commercial or open-source) such as AMPL, GAMS, Cplex, ... have a specific Algebraic modelling language. Some of them have another type of programming that uses ...
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