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PowerShell replacing cmd?
A new Windows 10 build has CMD largely (or somewhat) replaced by PowerShell. Typing CMD in the run box will also give you PowerShell. Will that affect CMD batch...
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NEOS GAMS Jobs
NEOS allows you to run GAMS jobs on a remote server, so you don’t need a GAMS system installed. The web based submission is a useful tool for self-contained models. That is when everything is in the...
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Reformulation of non-differentiable term
In a non-linear programming model with a rather complicated objective I see a term\[\frac{p}{2}\left(|x| + x\right)\]that is minimized. It is also noted that \(p>0\). From a picture of...
View ArticleHypo-Variance Brain Storm Optimization?
I never heard of this before, but here is a Matlab application. Looks like “Brain Storm Optimization” is yet another heuristic. (Not so easy to keep track, every academic seems to have the urge to...
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Table Assignment for Kindergartners
From this post we have a problem stated as:My wife teaches AM and PM kindergarten classes. AM has 14 students and PM 11. At the beginning of each month, she puts out a new seating chart where she...
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Cplex 12.7 and Benders Decomposition
The new version of Cplex (12.7) has some interesting new facilities to make it easier to use a Benders Decomposition approach (1,3). Paul Rubin shares some experiences with this in (2).The original...
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[VIDEO] A Huge Debate: R vs. Python for Data Science
Interesting video:[Video] A Huge Debate: R vs. Python for Data Science (presentation by Eduardo Ariño de la Rubia)Packages discussed:Collecting Data Feather (binary file format for storing data frames...
View ArticleManagement Science on Vox
Fuel is cheap. Why are we still paying to check bags? ReferencesMariana Nicolae and Mazhar Arıkan and Vinayak Deshpande and Mark Ferguson, Do Bags Fly Free? An Empirical Analysis of the Operational...
View ArticleReading CSV files in R: read.csv vs read_csv
There are a number of very fast CSV file readers available in R and Python. Lets have a quick test to see how they compare.Generating CSV fileI generated a very simple, but large CSV file with 100...
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Sorting inside a MIP model
This does not happen a lot, but in some cases we want to sort decision variables. This turns out not such an easy exercise.When not to use sortingIf we deal with just the \(\min()\) or \(\max()\)...
View ArticlePyMathProg: another Python based modeling tool
Project homepage: http://pymprog.sourceforge.net/Uses GLPK as solver. Here is a small example:frompymprogimport*c=(10,6,4)A=[(1,1,1),(9,4,5),(2,2,6)]b=(10,60,30)begin('basic')# begin...
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Multiple solutions in stylized flood planning model
For a project I was looking at a simple two stage stochastic integer programming problem (1). I find it always very rewarding to reproduce the results in the paper. Re-implementing the model forces me...
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New book: Optimization by GRASP; Greedy Randomized Adaptive Search Procedures
This is a well known meta-heuristic (with a somewhat less flashy name than some of the new heuristics that get invented every week). Apparently this is the first book fully dedicated to GRASP. GRASP...
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MonetDB and R
MonetDB (1) is a so-called column-oriented database or column-store (2). It is server based, SQL compliant and open-source. The column orientation can lead to better performance for certain types of...
View ArticleSAS/OR MIP solver
In (1) the performance of the SAS/OR MIP solver is discussed. It uses the MIPLIB problem set. Timings from different studies are always difficult to compare, but if we take the 214 or 218 feasible...
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Unique Solutions in KenKen
In (1) a MIP model is proposed so solve the KenKen puzzle. During a discussion, the question came up if I could prove the uniqueness of a solution. In the Mixed Integer Programming model I used a...
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MIP Modeling
In an investment planning model I needed to model the following:We can build a facility during any time period. So we have:\[\begin{align}&build_t \in \{0,1\} \\ &\sum_t...
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Smart Slime Mold on page 3 of the Washington Post
ReferencesWashington Post article: https://www.washingtonpost.com/news/speaking-of-science/wp/2016/12/30/the-strange-case-of-the-slime-molds-that-can-learn-and-teach-one-anotherSlime mold and linear...
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Solving Takuzu puzzles as a MIP using xor
The Takuzu puzzle (1) can be solved using a MIP model. Interestingly we can use an xor condition in the model. Assuming an \(n \times n\) board (with \(n\) even), we need to fill the cells \((i,j)\),...
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Solving LP by LU???
Yes, according to this paper [link]:Abstract This paper presents a new approach for the solution of Linear Programming Problems with the help of LU Factorization Method of matrices. This method is...
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