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1500 questions
14
votes
2 answers
Subtour elimination constraints - enumeration vs dynamically adding
The classical constraints to prevent subtours in routing problems (i.e., to make sure every route is connected to a depot), are of the following form,
$$
\sum_{(i,j) \in \delta(S)} x_{ij} \leq |S| - 1 \quad \forall S \subset V_C,
$$
where…
Albert Schrotenboer
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14
votes
1 answer
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 APIs to connect with general programming languages…
A.Omidi
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14
votes
3 answers
Dataset human solutions for OR problems
I would like to compare human solutions for OR-problems to optimal solutions. Therefore, I am looking for a dataset with the manual solutions computed by a human. I do not have a specific problem in mind, any problem would be nice.
Does such a…
Bgz6
- 191
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14
votes
5 answers
Non-OR journals which regularly publish OR research
I am looking for journals which do not focus on OR or a subfield (math programming, simulation, logistics, etc.) but still publish a few OR papers on a regular basis. What are some journals which would fit this criteria?
An example is Socio-Economic…
dxb
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14
votes
1 answer
Estimation of the size of Branch-and-Bound trees using ML
A short background:
A paper [1] published in 2006 intends to show that the time needed to solve mixed-integer programming problems by branch and bound can be roughly predicted early in the solution process. Authors mentioned that "The application of…
Oguz Toragay
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14
votes
3 answers
A variant of the Multiple Traveling Salesman Problem
I am trying to find a reference (or a reformulation) of a variant of the multiple Traveling Salesman Problem, where multiple agents need to visit each vertex in a graph with minimal cost.
Most of the literature that I found requires that only one…
kemalduldul
- 143
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13
votes
1 answer
Sum of Max terms maximization
Maximizing sum-of-max terms is an NP-hard problem. The objective function is a convex function and maximizing a convex function is a hard problem. Also, this is a non-differentiable function.
CPLEX and GUROBI solve these problems to global…
independentvariable
- 3,980
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13
votes
5 answers
What are technologies or libraries which greatly improve the speed or ease of use for delivering of OR software?
There are many great technologies/libraries out there to improve the speed and quality of implementing and deploying OR applications. However in my experience I "stumbled" upon many of them often by accident and they greatly improved the…
user3680510
- 3,655
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13
votes
3 answers
Are there any efficient algorithms to solve the longest path problem in networks with cycles?
I have a directed social network and as a preprocessing step I need to calculate the longest path lengths for each node. Longest path problem is NP-hard as far as I know but I've seen dynamic programming methods for DAGs. Is there such a method for…
Evren Guney
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13
votes
2 answers
Correct way to get a dual extreme ray for an infeasible LP in CPLEX / C++
We are coding a Benders decomposition using CPLEX/Concert (C++) and we are having some troubles to generate a feasibility cut because we are not sure how to get an extreme ray of the dual for a primal infeasible problem.
According to this CPLEX FAQ,…
Borelian
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13
votes
6 answers
Where can I find documentation on good practices for efficient formulations of a problem?
I am sort of new to mathematical optimization and have to build some fairly complicated models for my thesis. I was wondering where I could find literature to help me develop more efficient versions of them. I'm thinking of general good practices in…
J. Dionisio
- 534
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13
votes
3 answers
Efficiency of solving LP relaxation
I'm building a mixed-integer programming model, and the solver is experiencing a very long run time. So I tried to solve the LP relaxation to the MIP, and I get a similarly long solve time, which surprises me. I was wondering what might make an LP…
Yinan
- 379
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- 4
13
votes
5 answers
Connectivity of two nodes in an arbitrary undirected graph
Is there an efficient way to model the connectivity of two nodes in an arbitrary undirected graph? I would like to have a binary variable representing this connectivity: 1 if there exists a path between these two nodes and 0 otherwise. Let us assume…
Mertcan Yetkin
- 540
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13
votes
2 answers
Supply Chain Public Data Repository
I was wondering if there is any repository of datasets for supply chain problems. For example, the UC Irvine Machine Learning Repository contains datasets for ML, and MIPLIB is used as a benchmark for MIP and IP problems. But I cannot find a similar…
Afshin Oroojlooy
- 835
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- 15
13
votes
1 answer
Branch and Price algorithm is exact?
I know that the Column Generation algorithm delivers an exact solution when you are solving a linear programming optimization problem. I want to know that, does this column generation approach deliver the exact solution when integer variables come…
A.A
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