Gabriele Cosmo
82 lines
2.4 KiB
C++
82 lines
2.4 KiB
C++
// -*- C++ -*-
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//
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// -----------------------------------------------------------------------
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// HEP Random
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// --- HepStat ---
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// Purely static class containing useful statistics methods
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// -----------------------------------------------------------------------
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// HepStat is a substitute for using a namespace.
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// One would never instantiate a HepStat object;
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// usage of any of these methods looks like --
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//
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// double x = HepStat::erf ( .1 );
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//
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// A user may wish to improve the readability of algortihm code which uses
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// one method many times by lines like using HepStat::erf
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//
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// and later, x = erf(u); will work.
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//
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// These methods are implemented in separate .cc files so that
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// user code need pull in only the code that is necessary. Time
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// (ROUGH estimates in cycles) and table footprint info is provided
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// in this header.
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// =======================================================================
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// M. Fischler - Created: 1/25/00
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//
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// M. Fischler - Inserted flatToGaussian 1/25/00
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// From code of an attempt to speed up RandGauss
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// by use of tables and splines. The code was not
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// significantly faster than Box-Mueller, so that
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// algorithm is left as the RandGauss implementation.
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// - Inserted inverseErf
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// M. Fischler - Inserted gammln 2/4/00
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// M. Fischler - Made constructor private; removed private destructor 4/17/00
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// =======================================================================
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#ifndef HepStat_h
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#define HepStat_h 1
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namespace CLHEP {
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/**
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* @author
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* @ingroup random
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*/
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class HepStat {
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private:
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HepStat();
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// You CANNOT instantiate a HepStat object.
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public:
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static double flatToGaussian (double r);
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// This is defined by the satement that if e() provides a uniform random
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// on (0,1) then flatToGaussian(e()) is distributed as a unit normal
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// Gaussian. That is, flatToGaussian is the inverse of the c.d.f. of
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// a Gaussian.
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// Footprint: 30 K // Time: 150 cycles
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static double inverseErf (double t);
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static double erf (double x);
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// defined in flatToGaussian.cc
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static double erfQ (double x);
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// Quicker, and with less footprint, than erf and gaussianCDF
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// but only accurate to 7 digits.
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// Footprint: 0 // Time:
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static double gammln (double x);
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// ln (gamma(x))
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};
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} // namespace CLHEP
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#endif
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