Dear Rene I have also a question regarding TMath: I have a method, where I call floor or ceiling more than 500,000 times. Is there a reason why TMath::Ceil and TMath::Floor are not defined as inline methods? Would calling TMath::Floor instead of floor increase the execution time? Best regards Christian Rene Brun wrote: > Hi F.X, > > I have protected TMath::Acos and ASin in the CVS version. > > Rene Brun > > On Wed, 28 Apr > 2004, GENTIT Francois-Xavier DAPNIA wrote: > > >>Hello Rooters, >> >> >> >>Concerning the discussion about modifications in TMath, I want to report >>about a problem I had recently. Try the following (in CINT or in compile >>mode, it does not matter) >> >> >> >>--> Double_t a = 1.0; >> >>--> Double_t b = 4.0e-16; >> >>--> a += b ; >> >>--> Double_t c = TMath ::ACos(a) >> >> >> >> c is now equal to -1.#IND. If you are a purist, you will say ok, nothing >>wrong, because the ACos of a value bigger than 1 does not make sense. But >>such a small error as 4.0e-16 is normal when calculating in double >>precision. So that it happens! For me, it happened when doing the scalar >>product of 2 unit vectors which were parallel. And it does not crash the >>program, but the program continues delivering wrong results! >> >> This is a nasty problem which obliged me to derive a new ACos (and ASin) >>function with protections. >> >> >> >>F.X.Gentit >> >>DAPNIA/SPP CEA Saclay >> >>http://gentit.home.cern.ch/gentit/ >> >> >> >> > > > >
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