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1500 questions
8
votes
4 answers
Are simulations a form of multi-objective optimization?
Where is the line when an approach is called multi-objective optimization? For example:
Problem
Presume I want to optimize an optimization problem, for example nurse rostering, with 2 soft constraints:
Constraint A) for employee happiness: number…
Geoffrey De Smet
- 4,851
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- 34
8
votes
3 answers
Do you know production deployments of multi-objective optimization?
In mathematical optimization software, defining the weight and level (hard/soft) of each of the objectives/constraints is often difficult for the business people at software development time, due to the impact on different stakeholders. There are…
Geoffrey De Smet
- 4,851
- 10
- 34
8
votes
1 answer
Why is Gurobi output in Pyomo returning floating-point values rather than optimal integer solution?
I am hoping someone will be able to point me in the direction of why I am experiencing floating-point outputs rather than simply model.X = [15,15] and model.Z = [15,5] as solutions to this model?
Note that I use a piece-wise constraint to determine…
Jwem93
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8
votes
2 answers
Convert MPS file to the associated MIP model
I have a huge mps file and would like to get the associated MIP model, i.e., the objective, constraint, and bounds.
Is there any tools that could get that?
Afshin Oroojlooy
- 835
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- 15
8
votes
1 answer
Using the values of variable in the objective function before optimizing
I am facing a problem to multiply a term in objective function. My objective function is :
\begin{equation}
\min \sum_{t=1}^\top p_{t} \cdot (1+r) \cdot y_{t}
\end{equation}
where $p$ is the price, $y$ is the quantity (decision variable) and…
salidi
- 99
- 4
8
votes
1 answer
A variant of weighted perfect bipartite matching
I am currently working on weighted perfect bipartite matching, i.e., assignment problem.
Formally speaking, it could be formulated as follows:
$$
min \sum\limits_{i=1}^{N}\sum_{j=1}^{N}c_{ij}x_{ij}
$$
, where
$$
\sum\limits_{j=1}^{N}x_{ij} = 1…
Shinshin
- 83
- 3
8
votes
2 answers
Gurobi's "Out of memory" error without exhausting the RAM?
I wrote a branch-and-price algorithm in Python 2.7 which solves several small LP and MIP models by Gurobi 8.1 in each node. The algorithm runs fine at first, it produces both lower bound and upper bounds, solves all of the mentioned models many…
Mehdi
- 683
- 6
- 17
8
votes
2 answers
VRP through constraint programming
I am with a problem that consists of determining whether a VRP instance is feasible, this question is a continuation of an older thread.
In order to do it, I was thinking of using Constraint Programming (CP).
Since this is my first time using CP, I…
Matheus Diógenes Andrade
- 1,238
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- 14
8
votes
0 answers
Traveling Salesman Problem: determine k-exchange feasibility
Given a current solution $S$ and a $k$-exchange move $(v_1, .., v_{2k+1})$ with $v_1 = v_{2k+1}$, $v_i \neq v_j$, $(v_i, v_{i+1}) \in E(S)$ iff $i$ odd, i.e. we remove all edges $(v_i, v_{i+1})$ for $i$ odd and add all edges $(v_i, v_{i+1})$ for $i$…
fontanf
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8
votes
1 answer
Guides for strong MILP Formulations
When developing MILPs, often there are different alternatives possible to express a constraint. The question then arises, which of the alternatives is better, meaning, which alternative is expected to perform better during the solution process.
Is…
Clement
- 2,252
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8
votes
2 answers
Reference for algorithms and complexity
What kind of background in algorithms and complexity theory is needed to fully understand the computational aspects of an OR paper. To be specific, I am not always sure when a paper says 'XYZ problem is $\mathbf{NP}$ hard, or $\mathbf{NP}$ complete.…
superhulk
- 183
- 3
8
votes
2 answers
Does dispersion really matter?
Context:
Given a counting process $\{N(t),\,t\ge 0\}$ which tracks the number of events (arrivals) by time $t$, the index of dispersion (for counts) is the variance-to-mean ratio of the cumulative number of events (arrivals) by that point in time.…
SecretAgentMan
- 1,895
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- 39
8
votes
2 answers
Is $\min \ x^3 \ \mathrm{s.t.}\ x \geq 0$ a convex problem?
The problem $$\min \ x^3 \ \mathrm{s.t.} \ x \geq 0$$
is sometimes said to be a convex optimization problem. $f(x) = x^3$ is not a convex function. However, in the domain of $x\geq 0$ it is convex. So for some definitions this is a convex…
independentvariable
- 3,980
- 10
- 36
8
votes
1 answer
Real-life timetabling problems in education
I am looking for papers/resources that deal with timetabling problems in education. I want the resources to cover as much information as possible:
I don't have enough contact with people who are managing high schools. I cannot imagine all of their…
Best_fit
- 567
- 2
- 9
8
votes
1 answer
Assignment problem using Hungarian method
There are five jobs to be assigned to five machines and associated cost matrix is as follows
$$
\begin{matrix}
\text{Machine} & 1 & 2 & 3 & 4 & 5 \\
\text{Job A} & [11, &17, &8, &16, &20] \\
\text{Job B} & [9, &7, &12, &6, &15] \\
\text{Job C} &…
Tango
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