From kde-core-devel  Thu Nov 18 01:48:57 1999
From: Torben Weis <weis () stud ! uni-frankfurt ! de>
Date: Thu, 18 Nov 1999 01:48:57 +0000
To: kde-core-devel
Subject: Re: Need help for KSpread Maths
X-MARC-Message: https://marc.info/?l=kde-core-devel&m=94293575110896

Hi,

On Wed, 17 Nov 1999, Cristian Tibirna wrote:
> On Wed, 17 Nov 1999, weis wrote:
> 
> > Hi,
> > 
> > Excel has this "Goal Seek". Nice thing. You point it to a formular
> > and to the cell that is used as input and Excel finds the
> > input value that makes the formula result in a user specified value.
> > 
> > In fact that is the problem of finding x in f(x) = 0.
> > 
> > There are many algorithms which help you here, but they want
> > a) a range [a,b] to search in which can be very big with double values.
> > b) two points a and b, so that f(a)*f(b) < 0.
> > 
> > Can anyone tell me what to do here. Excel is getting quick and good
> > results, so there must be a way.
> > 
> > Bye
> > Torben
> > 
> > PS: No algebraic solutions.
> 
> Seems like this is a job for me.
> 
> Torben, is this pressing? I have to fix kikbd first, and work on kwin in
> the meanwhile. But I'd really like to do this numeric kind of things since
> this is my real-life job: numerical simulation. I believe for more general
> situations a Simplex algorithm will do. 
> 
> If it is very important to avoid local optimums, we can look at Simulated
> Anealing.
> 
> Of course, I'd better do this in kscripts and have them pluggable.
> 
> Does anybody know excel's Solver? It's highly used by engineers and I'm
> sure we can do even better.
> 
> Cristian

I started all this because of your request Cristian :-)

So if you can help with a cool algorithm that would be just perfect.
Just go ahead an implement it in C/C++. I will care to calculate
f(x) if you give me x.

Bye
Torben