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Re: Stt external library glpk [message #10155 is a reply to message #10146] Tue, 09 February 2010 13:33 Go to previous messageGo to previous message
Gianluigi Boca is currently offline  Gianluigi Boca
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Registered: March 2004
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Stefano Spataro wrote on Tue, 09 February 2010 09:40


And another question: do we really need to use glpk inside our code? I suppose root classes are doing the same job, or maybe there is another reason?


Hi,
yes there are a couple of essential reason.

As far as I know there is no equivalent to GLPK in root.

GLPK is a pakage for performing minimizations of some function that is linear in the parameters to fit AND ALSO in the case when some of the parameters are INTEGER variables.

This branch of the minimization programming is called Mixed Integer Linear Programming (MILP) as I explained in many presentations on the STT pattern recognition.

So GLPK is a package for doing MILP.

The main reason why I chose it is that it is superfast compared to Minuit, so I can use it in the pattern recognition.

Also MILP has the nice feature that, thanks to the use of some integer variable, enables to :
a) resolve the left-right ambiguity typical of the straw tubes;
b) eliminate those hits which are clearly noise, authomatically already in the fit.

Without GLPK the STT real pattern recognition doesn't work.

Cheers Gianluigi
 
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