Re: [Help-glpk] Generate data section files for model (in GNU MathProg or other languages)

[Tony Khosravi]

Thank you for the answer Robbie,

2012/5/9 Robbie Morrison <address@hidden>

Hello Tony

------------------------------------------------------------
To:           address@hidden
Subject:      [Help-glpk] Generate data section files for model (in GNU
MathProg or other languages)
From:         Tony Khosravi <address@hidden>
Date:         Wed, 9 May 2012 17:13:36 +0200
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> Hi,
>
> I would like to know if it was possible to generate any
> data files in the GNU MathProg format with the GLPK
> lib.
>
> When I am talking about data file, I mean the data
> section of model data.  The aim would be to be able to
> generate many text files containing only the data
> section so that they can be used later with the solver
> and a file containing only the model section. I didn't
> find any thing like that.
>
> My thought is now to try to implement a general lib to
> generate sets or parameters in a text file according to
> the documentation gmpl, but I was wondering it this had
> been done before (which might be probable).
>
> I also had the idea of using the table statement with
> the CSV driver, but apparently, it cannot be used in
> the data section, only in the model section, and I
> don't want to touch the file with the model. The aim is
> to keep the data section separate from the model
> section.
>
> --

> *Tony Khosravi Dehkourdi*

>
> MSc. Student - Computer Systems

> *Link?ping University*
> El?ve ing?nieur -- G?nie Informatique, Syst?mes et R?seaux d'Informations
> (GI06)*
> Universit? de Technologie de Compi?gne*

> Tel:+46 7 60 69 51 57

Hello Tony

AFAIK, once your high-level MathProg model has been
translated into a low-level problem object, it is not
possible to detranslate it.

So I guess you are talking about doing this processing
before your MathProg model + data has been irrevocably
translated.

You may therefore need to do this work outside of GLPK?
That is my best guess anyway.

These links might be useful while thinking about your
problem:

 http://en.wikibooks.org/wiki/GLPK/Steps_of_GMPL_File_Processing
 http://en.wikibooks.org/wiki/GLPK/Interoperability
 http://en.wikibooks.org/wiki/GLPK/Scripting_plus_MathProg

best regards
---
Robbie Morrison
PhD student -- policy-oriented energy system simulation
Technical University of Berlin (TU-Berlin), Germany
University email (redirected) : address@hidden
Webmail (preferred)           : address@hidden
[from Webmail client]

I would say that the last link is partially the answer to my question.

I will try to explain better what I want to do.

So as I said, I would like to generate a file containing only data section through a program in a way that I can generate many of those data files through a program, and then run the GLPK solver on each data file according to a model. So you understand that the data section and the model section are in two different files. 

I think I need to say that I program in C++. 

Let's say that my program is split into three modules:
   - one which generates data (the nature of those data are not important) through N iterations
   - one which would store those data into  N files (data section in a text file)
   - one which read those data files one by one and run the solver (given a file which contains the model section)
The first and third modules are implemented, so I am interested in implementing the second one.

In fact, the aim is not to have a very flexible program since to be able to generate the data files, it (I) need to know the model. 
Let's say that my first module generate a matrix. With this matrix, I want to compute different things which would corresponds to some parameters needed for the model. Therefore, I would like to store them in file. In order to have something a bit flexible, I was wondering if there was some methods available in GLPK or in another library which could perform those action like a method called "toGMPLParam(name, defaultValue, listOfRecords)" 
which would give in a file in the GMPL format
param name default defaultValue record1, record2, ..., recordsN

It is still unclear I think so I will try to explain with an example as follow: 
I have this "program" in whatever-the-language
/* myprog.cpp */

begin
     // Here I generate some data that I store in a matrix
     var myMatrix <- generateData
     // Here I perform some operations on this matrix
    var var1 <- action1(myMatrix)
    var var2 <- action2(myMatrix)

    // Here is the part I am interested in
    fileOpen("mydata.dat")
    f <- toGMPLParam("var1", 0, var1)
    f <- toGMPLParam("var2", 0, var2)

    // I run this file with the solver and a .mod file
    var optimalSolution <- solve("mydata.dat", "mymodel.mod")

end

/* eof */

I am aware of the fact that I could implement a way of just writing those data in a file, trying to respect the MathProg format (as long as it is modular, I would be satisfied), but maybe GLPK or another lib provides such methods that would generate a file with the proper syntax used in MathProg given some parameters.

Best regards


-- 
Tony Khosravi Dehkourdi

MSc. Student - Computer Systems
Linköping University
Elève ingénieur -- Génie Informatique, Systèmes et Réseaux d'Informations (GI06)
Université de Technologie de Compiègne
Tel:+46 7 60 69 51 57