# Tag Info

29

I like to introduce students to the need for optimization algorithms by talking about the traveling salesman problem (TSP). I introduce the problem statement, which is easy to do, then let them brainstorm ways to solve it. Usually students suggest methods that are similar to nearest neighbor, etc. Eventually, someone usually says something like: If we're ...

20

Some results are highlighted below. There is one similar to the Braess paradox. In the paper by Spieksma and Woeginger, a paradox is proposed in which: Increasing the speed of some machines in a no-wait flow-shop instance may actually worsen the optimal makespan. We construct instances for which the ratio between optimal makespan with improved speed and ...

17

Finding the shortest path from A to B on a network is easy enough that a high-schooler can do it with pen and paper (Dijkstra's algorithm). Finding the longest path (without repeats) is much harder. (I once edited a maths textbook where the authors had assumed that a longest-path algorithm would be a simple modification of Dijkstra's algorithm. Noooope.)

14

The INFORMS Transactions on Education is devoted to works about education in OR. There you can find many cases already used by teachers in their courses, along with material for instructors.

14

One nice similar result I have seen in the Open shop scheduling problem, where Three is easy, two is hard! In the paper Gribkovskaia et al. (2006), they write: "In discrete optimization the complexity of a problem often increases dramatically when a numerical parameter changes its value from 2 to 3. Fascinated with this issue, Eugene Lawler wrote: “Sad to ...

12

I belatedly realised that we've missed one of the most famous OR paradoxes of all: In WW2, the Statistical Research Group at Columbia University considered the problem of how best to protect bombers from enemy fire. They observed patterns of bullet and shrapnel damage on bombers returning from missions over Europe. The obvious interpretation of these ...

11

One neat example is in the context of network design problems and is brought about by the concept of a Steiner node. In brief, a Steiner node is an auxiliary node that may or may not be included in a particular network design problem (say, a spanning tree or a survivable network design problem). Why would you ever need such a thing, since presumably adding ...

9

Consider a transportation problem with positive cost for all arcs. Now consider an augmented problem which is identical to the original, except there is an increase in supply at one origin, and an increase in demand by the same amount at one destination. The optimal cost of the augmented problem can be less than for the original. See EXERCISE 16 in the ...

9

There are lots of resources that contain optimization models and whose codes. Some of them are as follows: 1) Supply chain: Operations and supply management: The core A deep dive into strategic network design 2) Scheduling and manufacturing: Introduction to Computational Optimization Models for Production Planning in a Supply Chain Scheduling in Supply ...

8

While it may seem reasonable to think that costs increase when you increase production, the transportation problem only considers the costs of moving things around. As a consequence, increasing production may provide opportunity to change how things are moved around, and that may help save costs. For problems like this, is it often useful to think about an ...

7

Not a question, but switching to a reference management software has helped me a lot (Mendeley, in my case, but there are alternatives). In particular, the ability to tag papers with my own keywords, filter them based on my tags, and then sort them chronologically has helped me quickly get a better idea of the progress in specific areas of research. E.g. I ...

6

In my opinion the following result is counter intuitive. At least it was for me when I started studying OR. If you study probability theory, you typically start by manipulating discrete laws which are intuitive and easy to grasp, for example when you study the probability of getting a certain deck of cards, or a certain combination of balls from an urn. ...

5

The way I discover literature is to identify the key authors & papers in the field I'm interested in. From there on it's just a matter of following the citation trail. The influential authors/papers tend to be better written as well, which really helps when people are starting up.

5

A very interesting paper entitled: Analysis of flow shop scheduling anomalies has been recently published by Panwalkar & Koulamas (2020)1, that introduces the following anomalies: 1- Type 1 Anomaly: An increase of the processing time of a single operation in an optimal schedule causes a reduction in the optimal objective function value. 2- Type 2 ...

5

I think for business students looking at papers (for example from Interfaces) might be asking too much. If this is about getting business students to use OR tools, specifically MIP solvers, I would recommend the book "Model Building in Mathematical Programming" by H. Paul Williams. It mostly consists of case studies from various fields and is easy enough ...

4

My question is : for teaching purposes, what would be the best way to explain this paradox in simple terms ... how to explain what is going on from a more physical point of view ? One of the easiest examples to explain and visualize is the iron ore trains of Sweden. The trains hauled by Iore-class locomotives from Riksgränsen on the national border to the ...

4

Someone recently pointed me to a journal article about the movement of shoppers in a supermarket. A point of interest is that markets apparently use RFID technology to track shopper movements. If you could get a market (or market chain) to provide you with anonymized movement data and maybe store layouts, you might be able to have the students simulate ...

3

Many real-world datasets can be found using the google search engine dedicated to the dataset search in this web address. For example, you can use the datasets about the airports instead of restaurants, or you can search for 'Simulation Data' to find interesting datasets ready to be used in a simulation project.

1

The Concorde TSP solver comes with a nice GUI which visualizes the optimal TSP tour. Moreover, it also has several TSP-heuristics such as Greedy, Nearest Neighbor or Random-generation implemented. This makes it easy to visually compare heuristics and optimal solutions. According to their website the solver "has been used to obtain the optimal solutions to ...

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