Questions tagged [gams]
For questions related to GAMS (General Algebraic Modeling System), a high-level modeling system for mathematical optimization.
38
questions
1
vote
1
answer
52
views
custom branch and bound on cplex or GAMS
Does anyone have an idea how to create a custom B&B on CPLEX or GAMS? In my work, I need to add custom cuts on integer solutions in certain conditions by adding only one branch. Also, I need to ...
0
votes
0
answers
56
views
How to initialize a parameter (belonging to the first stage model) in a two stage model, taking its value from second stage model?
I am working on a two stage approach in order to reduce the complexity of a scheduling model which is an NP-hard problem. I have to implement a while loop in order to repeat solving the models in case ...
- 131
2
votes
1
answer
156
views
How to pass the values of a variable of the first model to a parameter of the second model?
I am working on a scheduling problem which is NP-hard problem. Therefore, I decided to implement two-stage strategy to speed up the solution process. I need to pass the values of a variable from the ...
- 131
3
votes
2
answers
232
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Convex equivalent of a constraint
I have a constraint as follows in my MILP model:
$$
\sum_{e} (a_1(e) - a_2(e))^2 \leq M
$$
Where, $a_1(e)$ and $a_2(e)$ are binary variables. Would you please guide me how can I find the equivalent ...
-2
votes
1
answer
135
views
How to print/display a specific element of a set in GAMS?
I have the follwoing set in GAMS
set i /10,13,15/;
how can I display the second element of this set ?
- 1,378
1
vote
0
answers
25
views
Using Neos Server to submit GAMS file
When I submit a GAMS file along with a GDX file to the Neos Server upon clicking the submit button I don't get any error but the following webpage which is not loading and nothing is displayed. I ...
- 163
3
votes
5
answers
782
views
Convert MCP model from GAMS to Pyomo
I have a Mixed Complementarity Problem (MCP) that represents a market under perfect competition. The model is written in GAMS and works as expected. But when translating it to Python, using Pyomo, the ...
- 315
2
votes
1
answer
308
views
gams syntax issue - "set identifier or quoted element expected"
Writing some GAMS code, getting some syntax errors:
Anyone recognize the problem?
- 181
2
votes
1
answer
201
views
How to solve infeasible cplex model in GAMS?
I am facing this kind of error
"Row 'eq1(14)' infeasible, all entries at implied bounds"
in a problem that a GAMS script gets data from MATLAB. I have seen some posts about conflict ...
- 21
2
votes
1
answer
62
views
Piecewise constraints in GAMS
I'm trying to solve the network problem below in GAMS Cplex. I have a piecewise constraint that are depending on the node situations (whether a node is an origin (o) node, inbetween node, and ...
2
votes
1
answer
157
views
multiple solutions to a nonlinear problem in GAMS
Good afternoon, I have the following doubts
Is there a command in GAMS that lets me know when my problem has multiple optimal solutions?
Suppose my nonlinear optimization problem has multiple global ...
- 193
5
votes
3
answers
2k
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Is it better to use GAMS or Python for Optimization Models?
I have been using GAMS for several years, and I would like to do my new research in Python programming language. It is simple to do coding stuff in GAMS, however, it takes much time in complex ...
- 149
3
votes
2
answers
631
views
Write constraints with relationship sets in Pyomo
I would like to write the following constraint in the most compact form possible using Pyomo.
$$\sum_{o\in O}y_{n,o} = \sum_{o\in O} \sum_{n'\in LN}y_{n',o}\qquad \forall n$$
Where, the important part,...
- 81
2
votes
0
answers
135
views
Defining a highly non-linear function of integer variables
I have a complicated non-linear objective function of positive integer variables subject to linear constraints:
$\mathop {Min}\limits_{\underline x} f(\underline x)$
s.t.
$A\underline x\leq \underline ...
1
vote
0
answers
61
views
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 ...
- 11