Hello Yingjie
> ------------------------------------------------------------
> To: Andrew Makhorin <m...@gnu.org>
> Subject: [Help-glpk] variable object and deletions
> Message-ID: <259296.1916...@web54207.mail.re2.yahoo.com>
> From: Yingjie Lan <lany...@yahoo.com>
> 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
---
Robbie Morrison
PhD student -- policy-oriented energy system simulation
Technical University of Berlin (TU-Berlin), Germany
University email (redirected) : morri...@iet.tu-berlin.de
Webmail (preferred) : rob...@actrix.co.nz
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