Operations Research Stack Exchange
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Trying to keep MILP model small

Lets assume a complex production system that is fed by tasks of type $A$ (e.g. $A$ = deliver material) . Within a horizon of interest $H$, a number $N$ of tasks $A$ can be performed. The model of the problem results in a difficult MILP. Solving the…
Clement
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Issue of Dense columns in the formulation

I'm working on a price-selection model where we need to identify price point for each time-period (could be day/week). Objective of the model is to figure out optimal price-point for each time-point to optimize revenue from all products. One…
anjikum
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Minimize $\int_0^\infty g'(x)f(x)\,dx$ where $f(x)$ has a log-normal density

I would like to optimize (minimize) the following expression in order to find the functional minimizer $g$ (which should be at least once differentiable): $$ \int_0^\infty g'(x) f(x) \ dx $$ where $f(x)$ is the density of the log-normal…
Jay
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What kind of data structure should be used to store labels when implementing a labeling algorithm?

The shortest path problem with resource constraints is a common subproblem when doing column generation. It is often solved with a labeling algorithm. The procedure is very well explained here and here. To avoid complete enumeration, dominance is…
gmn
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Binary variable switch constraints

I have a set of binary variables $X = \{ x_1, x_2, x_3, ... x_N \}$ which are connect and used with the rest of the model. I want to define a set of binary variables which represents the change between the variables in $X$ with adjacency. Let this…
CharcoalG
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Confusion Between Different Types of Optimization Problems

I do not have a background in optimization and I am trying to teach myself more about this topic. I find myself having a lot of trouble understanding the different "types" of optimization problems that exist. For example, I understand the idea of…
stats_noob
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Integer Programming Constraints - Min/Max Days Between Deliveries

I'm starting a consulting project for a client who manufacturers perishable food. They want to optimize their delivery schedule to each of their DSD (Direct Store Delivery) customers. For each store, I have binary decision variables that reflect…
Ralph Asher
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"Types" of Problems where Evolutionary Algorithms (significantly) Outperform Non-Evolutionary Algorithms

In the field of Optimization and Operations Research : Are there "Types" any Problems where Evolutionary Algorithms (significantly) Outperform Non-Evolutionary Algorithms? For instance: Advancements in Machine Learning has shown us that problems…
stats_noob
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History of the (Famous) Simplex Algorithm?

What Real Life Problems Motivated the Creation of the (Famous) Simplex Algorithm? I was reading about the (famous) Simplex Algorithm : My Question: Were there any real world problems that people (e.g. Dantzig) were working on that required the an…
stats_noob
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I'm looking for materials to share with undergrads who want to consider a career or masters degree in OR

My daughter is a math major at a good liberal arts school. It doesn't seem like they have any OR courses or talk much about it as a career choice (either for a job or going to grad school in OR.) And, some of her friends at other schools who've…
Michael Watson
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Airline revenue management re-solving problem

I am considering a bid prices (shadow price of the capacity constraint) problem (from Chen, L. and Homem-de Mello, T. (2009)., page 14) where the acceptable classes for booking requests for itineraries need to be determined to maximize expected…
SimonCello94
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Multi-commodity Network Flow: Convert a node-arc solution to an arc-path solution

For a logistics optimization problem I am working on, the most natural expression of the problem is using a node-arc formulation of the MCNF. It is solved using an LP/MIP solver like CPLEX/Gurobi. However, for understanding the solution, the…
anerjee
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Lower bounds for TSP with k missing nodes

I'm struggling with this question for several weeks already and seem to be either stuck, or the bound is not going to be any better. Let's jump right into the problem: Given a standard TSP on a graph $G$ with $n$ nodes where the triangle inequality…
azaryc2s
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Python "Coffee Shop Scheduling Problem" - Scheduling Lunches/Breaks

I'm working on an employee scheduling program in python. Having never done this before, I've been researching different libraries that can be used to accomplish the task. Unfortunately, none of the examples I have been able to find for scheduling…
t25
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Optimize for bonuses within a group (knapsack)

I am trying to create an LP problem which is like the knapsack problem but with groups of items. Let's say there are 10 groups of items each with up to 5 items. Each group has one special item and you must choose only one, let's call that group the…
Eddie
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