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What is a submatrix? Contiguous?
I always thought that a submatrix is a contiguous part of a matrix. Like as shown in http://mathworld.wolfram.com/Submatrix.html.However in https://en.wikipedia.org/wiki/Matrix_(mathematics)#Submatrix...
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Finding a specific submatrix
From: http://math.stackexchange.com/questions/1542593/binary-integer-program-with-nonlinear-function/1559874#1559874:Here we mean by submatrix any set of columns (not necessarily contiguous). I can...
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1000 x 1000 assignment problem: 10 hours?
In http://stackoverflow.com/questions/34096450/how-to-increase-the-efficiency-when-you-have-1000x1000-matrix-in-excel a user reports that for a 1000x1000 assignment problem, OpenSolver takes more than...
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Modeling languages vs Matrix Generators
A famous paper by Bob Fourer “Modeling languages versus matrix generators for linear programming” (ACM TOMS, 1983) discusses the advantages of a modeling language (AMPL) versus the (then) traditional...
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A Model with Semi-Integer variables
Not many times I encounter a model where I can use semi-integer variables. These are integer variables that are either zero or some value between LO and UP. I.e. x ∈ 0 ⋃ {LO,..,UP}.The problem is as...
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Visualization of large multi-criteria result sets with plot.ly
Plot.ly is a great Javascript based visualization tool. Here I try to get a better understanding of a solution set of Pareto optimal points.These are the results of a three objective Multiple Objective...
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Visualization of large multi-criteria result sets with Bokeh
In http://yetanothermathprogrammingconsultant.blogspot.com/2015/12/visualization-of-large-multi-criteria.html we showed some 3D (interactive) plots using plot.ly. Here we look at a pair of 2D...
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Goat, wolf, cabbage
In this post the question was raised if we could solve the famous puzzle:(see: http://www.mathcats.com/explore/river/crossing.html). Here is my attempt: The ‘Eat’ table looks like: This is based on:...
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Coloring
With some help from here I can now dynamically change the coloring scheme of the data points: Here we color things according to z,y,x values and the distance to Utopia point (that point in the right...
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Non-convex QPs on a D-Wave Quantum Computer?
Here is an interesting suggestion for solving a non-convex Quadratic Programming problem.See also this post.
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Packing circles in a rectangle: a MIQCP model
An interesting problem was posed here. Given a set of circles (with given radius) try to cover as much area of a rectangle. Here the circles represent sensors.The circles may look more like ellipses as...
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Find subset with same mean
In this post the following problem is posed:Given a set of numbers with mean μ0 find a subset of at most K numbers that has a mean μ that is as close as possible to μ0. Of course we try immediately to...
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Internet Explorer WebGL bug
I was doing some experiments with a 2d scatter plot with more than 5k points (see http://yetanothermathprogrammingconsultant.blogspot.com/2015/12/visualization-of-large-multi-criteria_18.html for more...
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Finding all optimal LP solutions
I am regularly confronted with the question: My LP model has multiple optimal solutions. Can I retrieve all optimal LP solutions? Probably the correct answer on this question is: no. If there are...
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Finding all optimal LP solutions using the Cplex Solution Pool
In http://yetanothermathprogrammingconsultant.blogspot.com/2016/01/finding-all-optimal-lp-solutions.html a MIP formulation was presented to enumerate all optimal LP bases. A loop construct was used to...
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Constraint Solving and Planning with Picat
Interesting book about an interesting language. I once had a copy of Turbo Prolog; Picat looks and feels similar in many respects.
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A variant of the Lights Out game
Suppose we have a grid like this, with some binary values turned on:This is our initial state s0. The goal is to turn all lights off, but there is a catch. When flipping a light switch all lamps in the...
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GAMS to Python (2)
A simple, convenient way to move model results from a GAMS model into Python for further postprocessing is via a SQLite database. This looks like a roundabout way but in practice it works quite well.To...
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Book buyers price index
We have the well-known CPI index, but may be we also need a separate index for people who buy books. Of course this also applies to journal papers. In this post I was encouraged to have a look at this...
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Simulating a color-bar in Bokeh
Bokeh does not (yet) have built-in support for color-bars. Below we simulate this by adding a figure below the scatter plot. Interesting to see how this is on the to-do list for a while:...
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