PHP+MySQL
While doing some work on a PHP+MySQL+JavaScript+GAMS+Excel+StatPlanet project:http://me.veekun.com/blog/2012/04/09/php-a-fractal-of-bad-design/http://grimoire.ca/mysql/choose-something-else
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There are 293 ways to make change for a dollar
Only if you include $0.50 coins and the dollar bill itself…$ontext There are 293 ways to make change for a dollar http://realfacts.snapple.com/dontgochanging/$offtextsets c 'coin (or bill)'...
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Meta-Heuristics or Math Programming (2): Comparing solutions
A well-known example data set for Generator Maintenance Scheduling (GMS) is the basis for quite a few computational studies using meta-heuristics. The data sets has 21 units, has time-periods of a week...
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Mean Absolute Deviation
This is a modeling construct I see re-occurring at regular intervals. One formulation is given here:http://www.princeton.edu/~rvdb/542/lectures/lec9.pdfI would typically write this slightly...
View ArticleExporting a Matlab matrix to GAMS
There are (at least) two ways to export data from Matlab and loading them into GAMS: using a CSV file or using a GDX file. Here is a small comparison with a large matrix (4 million entries): CSV...
View ArticleThere are 293 ways to make change for a dollar (2)
In a previous model we used cuts to find all solutions (http://yetanothermathprogrammingconsultant.blogspot.com/2013/03/there-are-293-ways-to-make-change-for.html). This time we use the solution pool...
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Hamming distance and persistent solutions
When building scheduling models it is often important to make sure that a new schedule is not radically different from an old schedule unless there is a very good reason (e.g. we can make a lot of...
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ArcGIS adventures
This is not yet really big data, but the data was large enough to cause some headaches. Different database formats start to fail when exceeding 2 GB file size limits. Old fashioned CSV helped, but we...
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Excel for Modeling
Excel is great for data entry and reporting, but as a modeling tool it may not always be the best choice. Here is a great...
View ArticleMore optimization in JavaScript
http://www.optimizationzen.com/2013/04/18/optimization-framework-js/Not sure if this model is as readable as I would like it to be. Not so easy to recognize a transportation model in this....
View ArticleRewriting GAMS code
A first attempt to write some code turned out to be correct, but very slow:cube('PPX0a.zip','Producer Price',cgroup,cname,y,indicator, '','','-','','','','',cty) =...
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Sparse matrix multiplication in SQL
This actually could work reasonably well:Source: http://research.microsoft.com/en-us/um/redmond/events/escience2012/Bill_Howe.pdfOther links:...
View ArticleScalar models
AMPL has since a long time facilities to write Constraint Programming models (see http://users.iems.northwestern.edu/~4er/WRITINGS/cp.pdf), but only recently this became available for the general...
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Quantum Computing vs Cplex
http://graphics8.nytimes.com/packages/pdf/business/quantum-study.pdfSummary: on some exotic hardware we can find good solutions (heuristic) for some combinatorial problems much faster than with Cplex...
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Long Strings
Should developers impose hard limits on lengths of strings? Yesterday struggled good part of the day to work around some issues where we needed long labels in GAMS. Looking back I think that in general...
View ArticleMicrosoft Update
Critical Information Regarding Microsoft Update and ArcGISA recent Microsoft update (deployed as KB 2732673, KB 2775511, or KB 2824408) may result in data corruption when using ArcGIS on a Windows 7...
View ArticleVisualization of Model Results
I was working on some sheets about visualization of results of policy models. Of course we cannot leave out Hans Rosling:
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Elements of Statistical Learning
Although the book is available as PDF file from http://www-stat.stanford.edu/~tibs/ElemStatLearn/ I decided to spend the $80 and ordered the book as real book. It was delivered this weekend. Some...
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Fodder
I am teaching an Intro GAMS class at a government agency, and I was thinking about doing a shortest path model as LP. There are lots of interesting angles from a modeling perspective, at least I think...
View ArticleData Models and Optimization Models
Just had another example of what I see more often. In this case we deal with a fairly small data model. Unfortunately the db guru has mixed up flow and stock variables. When developing a scheduling...
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