Hi Ken, Of course, I agree with your theory. I was just asking you to try to implement the one or few lines that you suggest, with no dramatic effect on the function behaviour. Take the current source from http://root.cern.ch/root/htmldoc/src/TMath.cxx.html#TMath:Poisson Rene Brun On Mon, 26 Apr 2004, Ken Bloom wrote: > Even a check to see that the function is returning a finite value > would be nice. If I remember my probability distributions correctly, a > Poisson probability has to be between zero and one, so it shouldn't return a > non-finite value. I believe that zero would be the right value to return if > the calculation gives a non-sensical number. Failing that, I'd even take > something where you test the input values, and if they are bigger than the > Gamma or Power functions could handle correctly, you give a printout that said > "Why are you trying to calculate a Poisson probability with such large > numbers, you fool!" Best wishes. > > Ken > > On Mon, 26 Apr 2004, Rene Brun wrote: > > > Ken, > > > > I will be happy to add any suggestion you might have to protect the code > > against the case you mention. > > > > Rene Brun > > > > On > > Mon, 26 Apr 2004, Ken Bloom wrote: > > > > > Dear ROOTers, > > > > > > I'm using ROOT 3.05/07, and am getting non-numerical results out of > > > the TMath::Poisson function, under what I admit are extreme conditions: > > > > > > root [2] TMath::Poisson(170,70) > > > Error: Symbol inf is not defined in current scope FILE: LINE:0 > > > (Double_t)inf > > > *** Interpreter error recovered *** > > > > > > Yes, I know that the result should be a very tiny number, but I would prefer > > > that I get 0.0 (or its moral equivalent) rather than something I can't do math > > > with. Can you recommend a protection against this? Thanks, best wishes. > > > > > > Ken Bloom > > > > > > ------------------------------------------------------------------------------ > > > Ken Bloom, Karma Adjuster Department of Physics > > > 734-763-2329 / 734-936-1817 (fax) University of Michigan > > > kenbloom@umich.edu http://www.umich.edu/~kenbloom > > > > > > > ------------------------------------------------------------------------------ > Ken Bloom, Karma Adjuster Department of Physics > 734-763-2329 / 734-936-1817 (fax) University of Michigan > kenbloom@umich.edu http://www.umich.edu/~kenbloom >
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