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Visualization: Animating flow along an edge
In a large network, it is a bit of a pain to visualize the flow. Here is an attempt to show the shortest path in a random sparse directed graph. The shortest path is of course a min-cost flow of one...
View ArticleSLSQP original paper
This is somewhat hard to find (although I did), so I share it. This is the original paper[1] describing the SLSQP solver used in scipy[2]: To download use the menu button at the bottom and choose...
View ArticleWanted: better error messages
In [1] a user tries the following constraint: mdl.addConstrs((t[i,k] * X[i,j,k] - te1[i] <= 5) >> (z1[i,k] == 1) for i,j,k in arcos if i != 0 and i != 23)(t and X and variables). This is not...
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Bostock's command-line cartography tutorial under Windows
In [1], an excellent tutorial is presented about the process of making maps. It is a little bit dated, so here I develop some Windows-based scripts that make it possible to follow these tutorials. The...
View ArticleRewriting old GAMS code
It is always a good idea to revisit existing GAMS code and see if we can improve it. Here is an example of an actual model.The problem is that we want to set up a mapping set between two sets based on...
View ArticleGAMS: Undocumented PUT formats
The GAMS documentation mentions f.nr=1 (standard notation) and f.nr=2 (scientific notation) for formatting numeric items using the PUT statement. There are however a few more. Here we print values...
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Expanding Visual Studio in the Task Manager
This is scary. Note that is in an idle state (nothing compiling, running, or debugging at the moment). Soon we all need 128 GB of RAM.
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Inverting a large, dense matrix
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View ArticleGetting rid of non-linearities
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Evil Sudoku
On sudoku.com[1] there is now an "evil" difficulty level. I found these very difficult to solve by hand (I usually give up). Of course, a good MIP presolver/preprocessor devours this in no time. It...
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Ranking using numpy.argsort
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View ArticleCoding is to programming like typing is to writing
Quote by Leslie Lamport: Coding is to programming like typing is to writingMy generalization: IMHO, developers often start coding (i.e. typing) way too early.
View ArticleA subset selection problem
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View ArticleMaximizing Standard Deviation
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MAX-CUT
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View ArticleGoal Programming
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View ArticleXNOR as linear inequalities
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Artificially creating a large LP model: why is Cplex so efficient
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View ArticleTransportation model with some non-existing links
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View ArticleLinearize min(a,b)>min(x,y)
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