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Re [Help-glpk] variable object and deletions

From: Robbie Morrison
Subject: Re [Help-glpk] variable object and deletions
Date: Wed, 20 Jan 2010 18:58:20 +0100
User-agent: Thunderbird (X11/20080306)

Hello Yingjie

> ------------------------------------------------------------
> To:          Andrew Makhorin <address@hidden>
> Subject:     [Help-glpk] variable object and deletions
> Message-ID: <address@hidden>
> From:        Yingjie Lan <address@hidden>
> Date:        Mon, 18 Jan 2010 23:36:41 -0800 (PST)
> ------------------------------------------------------------
> Hi,
> Suppose you would like to use a variable object (a C
> structure, or C++ class, or Python class, etc) to
> represent a column in GLPK, it is probably natural to
> let the variable object have an integer field called
> 'index', which is the index of this variable in the
> GLPK model (the API of GLPK use this index very
> often). But there is a problem: when you delete a
> variable, you must update all this field for all
> variables behind the deleted variable. I am also aware
> of another index, which is the name of each variable,
> but it is less efficient (probably OK if doing
> Python). I wonder if there is a more elegant way to
> implement a variable object that would significantly
> brings down the overhead involved with variable
> deletions. Similar problem can be proposed for
> constraints, of course, and I suspect the solution is
> similar too.
> Regards,
> Yingjie

I assume this is during problem building and prior to
loading the data into a GLPK problem object?  For C++:

What if you hold your columns in std::list<Column>
rather than std::vector<Column>?  Easier to delete
entries in the way you wish I would think.

I haven't got any C++ books here, otherwise I would
work this up a bit more.

Berryhill will undoubtedly have some good suggestions
on the design of optimization problem structures:

  Berryhill, John B.  2001.  C++ scientific programming :
    computational recipes at a higher level John Wiley and
    Sons, New York, USA.  ISBN 0-471-41210-4.

hope this is on the right track
Robbie Morrison
PhD student -- policy-oriented energy system simulation
Technical University of Berlin (TU-Berlin), Germany
University email (redirected) : address@hidden
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