Double_t 4-momentum
[u/mrichter/AliRoot.git] / PYTHIA6 / AliPythiaRndm.cxx
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7cdba479 1/**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
3 * *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
6 * *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
15
16/* $Id$ */
17
18//-----------------------------------------------------------------------------
19// Class: AliPythiaRndm
cef490e6 20// Responsibilities: Interface to Root random number generator
21// from Fortran (re-implements FINCTION PYR from PYTHIA)
22// Very similar to AliHijingRndm
23// Collaborators: AliPythia and AliGenPythia classes
24// Example:
25//
26// root> AliPythia::Instance();
27// root> AliPythiaRndm::SetPythiaRandom(new TRandom3());
28// root> AliPythiaRndm::GetPythiaRandom()->SetSeed(0);
29// root> cout<<"Seed "<< AliPythiaRndm::GetPythiaRandom()->GetSeed() <<endl;
30//
7cdba479 31//-----------------------------------------------------------------------------
32
090026bf 33#include <TMath.h>
cef490e6 34#include <TRandom.h>
7cdba479 35
36#include "AliPythiaRndm.h"
37
38TRandom * AliPythiaRndm::fgPythiaRandom=0;
39
40ClassImp(AliPythiaRndm)
41
7cdba479 42
43//_______________________________________________________________________
44void AliPythiaRndm::SetPythiaRandom(TRandom *ran) {
45 //
46 // Sets the pointer to an existing random numbers generator
47 //
48 if(ran) fgPythiaRandom=ran;
49 else fgPythiaRandom=gRandom;
50}
51
52//_______________________________________________________________________
53TRandom * AliPythiaRndm::GetPythiaRandom() {
54 //
55 // Retrieves the pointer to the random numbers generator
56 //
3cdd391f 57 if (!fgPythiaRandom) fgPythiaRandom=gRandom;
7cdba479 58 return fgPythiaRandom;
59}
60
61//_______________________________________________________________________
6889dd2d 62#define pyr pyr_
63#define pygauss pygauss_
64#define pyrset pyrset_
65#define pyrget pyrget_
7cdba479 66
67extern "C" {
6889dd2d 68 Double_t pyr(Int_t*)
69 {
eb4da7a7 70 // Wrapper to FUNCTION PYR from PYTHIA
6889dd2d 71 // Uses static method to retrieve the pointer to the (C++) generator
72 Double_t r;
73 do r=AliPythiaRndm::GetPythiaRandom()->Rndm();
74 while(0 >= r || r >= 1);
75 return r;
76 }
77
78 Double_t pygauss(Double_t x0, Double_t sig)
79 {
80 Double_t s = 2.;
81 Double_t v1 = 0.;
82 Double_t v2 = 0.;
83
84 while (s > 1.) {
85 v1 = 2. * pyr(0) - 1.;
86 v2 = 2. * pyr(0) - 1.;
87 s = v1 * v1 + v2 * v2;
88 }
89 return v1 * TMath::Sqrt(-2. * TMath::Log(s) / s) * sig + x0;
90 }
91
92 void pyrset(Int_t*,Int_t*) {}
93 void pyrget(Int_t*,Int_t*) {}
7cdba479 94}