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Playing with job shop problem ft10 (4)
We could not solve my job shop formulations in http://yetanothermathprogrammingconsultant.blogspot.com/2014/04/playing-with-job-shop-problem-ft10-2.html but actually Or-tools has a pretty good C++...
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Playing with job shop problem ft10 (5)
In http://yetanothermathprogrammingconsultant.blogspot.com/2014/04/playing-with-ft10-job-shop-1.html we saw Gurobi was very successful in solving ft10.gms to optimality. How would the open source...
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How do they make a bug like this?
For a small project I needed to solve a very small QP model. As the input and output were in Excel, it made some sense to try Excel’s Solver. One of the constraints is: The way to do this is to create...
View ArticleReporting infeasible LP solutions in GAMS
When debugging models, one strategy that can be very helpful: fix a number of variables to a known (feasible) solution, solve, and inspect the reported infeasibilities. The known solution can be...
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Generating Larger Pivot tables in Excel from GAMS
I was working on generating some very large pivot tables to view model results. Some issues came up. Users tend to use things differently than expected: they may download and install 64 bit versions of...
View ArticleAnalytics for journalists
In http://thenextweb.com/apple/2014/06/02/apple-announces-swift-new-programming-language-ios/:The company says that Swift apps are significantly faster than Objective-C apps, outperforming them by over...
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Big data cubes
When exporting some large solution sets from GAMS I was wondering about the size improvements we can get by storing strings in a pool.The output data is organized in a very large “cube”, i.e. a single...
View ArticleA little bit extra fine tuning
Sometimes it helps to revisit old code and see if we can do better:--- Job compare.gms Start 07/01/14 23:12:51 24.2.2 r44857 WEX-WEI x86_64/MS Windows GAMS 24.2.2 Copyright (C) 1987-2014 GAMS...
View ArticleOuch
From: http://wwww.gams.com/mccarl/newsletter/news35.pdfPDF if the probability of a point is needed
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Old Fashioned SQL scripts
The tools gdx2sqlserver has an option to generate SQL scripts to populate a SQL Server database from GAMS data. (It has many other ETL facilities including bulk operations for high performance)....
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Excel Solver Error Message
Error messages really need to be formulated with care. I am already confused my code does not work and I would like to see a message that clearly states what is wrong and what I should do to remedy the...
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Coin CBC command line
For a small project I was trying out the binary distribution of COIN-OR’s CBC. The good news, it can solve the problem quickly (provided I allow a reasonable gap). I encountered a few issues: The...
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When do two intervals overlap?
For a scheduling tool I encountered the following problem. For a set of intervals generate a list of a pairs that overlap. For those pairs (A,B) I can generate a constraint (Note: we are smart and do...
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Experiment: Database Diagram of GAMS model
It is always helpful to look at your model in a different way. Not sure if this is a very useful tool in practice. But it may help when passing on data from a GAMS model to a DBA as a documentation...
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Data manipulation in GAMS, R or SQL
When moving data from GAMS to R via SQLite we have three possible spots where we can apply some data manipulation:Suppose we want to plot some data but need to do:Here is the code in GAMS:I could do...
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GAMS to Python
When we need to export data from GAMS to Python for further processing, I often use SQLite as intermediate storage. It is very easy to load data from SQLite into a Pandas dataframe: The text_factory...
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MIQP vs MIP
On my experience many MIQP models can and should be reformulated into straight linear MIP models. The reason is threefold: MIQP solvers are not as reliable as MIP solvers (they can experience numerical...
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Handling of inventory
In this book and the accompanying web site we see some unusual ways to model inventory. In the first chapters, inventory is not dealt with explicitly and therefore we look at equations such as:I.e. we...
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