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List:       kde-core-devel
Subject:    Re: Need help for KSpread Maths
From:       Roberto Alsina <ralsina () unl ! edu ! ar>
Date:       1999-11-18 19:40:41
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On Fri, 19 Nov 1999, Don Sanders wrote:

> On Thu, 18 Nov 1999, Roberto Alsina wrote:
> > On Thu, 18 Nov 1999, Antonio Larrosa wrote:
> > 
> > > Roberto Alsina wrote:
> > > > 
> > > > > I tried some polynomials I couldn't get it stuck in a cubic, which
> > > > > indicates it has at least some smarts for getting out of/avoiding rel.
> > > > > extrema. I did manage to get it stuck in a sixth order polynomial
> > > > > which indicates it isn't that smart. (Numerical solutions for finding
> > > > > the roots of any (finite) ordered polynomial to arbitrary precision
> > > > > exist).
> > > > 
> > > > Maybe it uses multiple methods?
> Probably not too many. From using it I get the impression that every time it
> computes a new value for f(x) it recalculates the entire spread sheet including
> updating the screen to show new values for all cells.
> 
> It seemed pretty basic to me. Actually it began to annoy me as I didn't actually
> know what method it was using and it did fail quite often, it made me feel is
> if it was just a toy that couldn't be relied on for serious work.
> 
> (Maybe getting a bit offtopic for kde-core?)

Maybe, but at least it's geeky and may be useful for a KDE app ;-)

A quick search in www.microsoft.com for "solver" shows some intriguing
stuff!

For example, it seems the solver in Office 2000 is modular and
replaceable (you can replace it with a VB module, just what all numerics
expert recommend[1] ;-)

Anyway, MS is even kind enough to say what algorithm they use!

http://support.microsoft.com/support/kb/articles/Q82/8/90.ASP


--------------
   SUMMARY

   Microsoft Excel Solver uses the Generalized Reduced Gradient (GRG2)
Algorithm for optimizing nonlinear problems. This algorithm was developed by Leon Lasdon, of the
University of Texas at Austin, and Allan Waren, of Cleveland State University. 

   Linear and integer problems use the simplex method with bounds on the
variables and the branch and bound method, implemented by John Watson and
Dan Fylstra, of Frontline Systems, Inc.
--------------

I must confess I had never heard of this algorithm before.


[1] I can imagine the screaming: "Why can't I do it in FORTRAN!!!!"

 ("\''/").__..-''"`-. .         Roberto Alsina
 `9_ 9  )   `-. (    ).`-._.`)  ralsina@unl.edu.ar
 (_Y_.)' ._   ) `._`.  " -.-'   Centro de Telematica
  _..`-'_..-_/ /-'_.'           Universidad Nacional del Litoral
(l)-'' ((i).' ((!.'             Santa Fe - Argentina
                                KDE Developer (MFCH)
Not mad, but bound more than a madman is (Romeo and Juliet, Act I Scene II)

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