Gabriele Cosmo
195 lines
6.7 KiB
C++
195 lines
6.7 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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//
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// $Id:$
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//
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#if __clang__
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#if ((defined(G4MULTITHREADED) && !defined(G4USE_STD11)) || \
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!__has_feature(cxx_thread_local)) || !__has_feature(c_atomic)
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#define CLANG_NOSTDTLS
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#endif
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#endif
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#if (defined(G4MULTITHREADED) && \
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(!defined(G4USE_STD11) || (defined(CLANG_NOSTDTLS) || defined(__INTEL_COMPILER))))
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#include <cmath> // for log()
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#include <CLHEP/Units/PhysicalConstants.h>
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#include "G4MTRandGaussQ.hh"
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G4MTRandGaussQ::~G4MTRandGaussQ()
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{
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}
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G4MTRandGaussQ::G4MTRandGaussQ(const G4MTRandGaussQ& right)
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: G4MTRandGauss(right)
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{
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}
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G4double G4MTRandGaussQ::operator()()
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{
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return transformQuick(localEngine->flat()) * defaultStdDev + defaultMean;
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}
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G4double G4MTRandGaussQ::operator()( G4double mean, G4double stdDev )
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{
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return transformQuick(localEngine->flat()) * stdDev + mean;
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}
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void G4MTRandGaussQ::shootArray( const G4int size, G4double* vect,
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G4double mean, G4double stdDev )
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{
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for (G4int i=0; i<size; ++i)
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vect[i] = shoot(mean,stdDev);
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}
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void G4MTRandGaussQ::shootArray( CLHEP::HepRandomEngine* anEngine,
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const G4int size, G4double* vect,
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G4double mean, G4double stdDev )
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{
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for (G4int i=0; i<size; ++i)
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vect[i] = shoot(anEngine,mean,stdDev);
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}
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void G4MTRandGaussQ::fireArray( const G4int size, G4double* vect)
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{
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for (G4int i=0; i<size; ++i)
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vect[i] = fire( defaultMean, defaultStdDev );
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}
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void G4MTRandGaussQ::fireArray( const G4int size, G4double* vect,
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G4double mean, G4double stdDev )
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{
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for (G4int i=0; i<size; ++i)
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vect[i] = fire( mean, stdDev );
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}
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//
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// Table of errInts, for use with transform(r) and quickTransform(r)
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//
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// Since all these are this is static to this compilation unit only, the
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// info is establised a priori and not at each invocation.
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// The main data is of course the gaussQTables table; the rest is all
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// bookkeeping to know what the tables mean.
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#define Table0size 250
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#define Table1size 1000
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#define TableSize (Table0size+Table1size)
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#define Table0step (2.0E-6)
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#define Table1step (5.0E-4)
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#define Table0scale (1.0/Table1step)
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#define Table0offset 0
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#define Table1offset (Table0size)
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// Here comes the big (5K bytes) table, kept in a file ---
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static const G4float gaussTables [TableSize] = {
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#include "gaussQTables.cdat"
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};
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G4double G4MTRandGaussQ::transformQuick (G4double r)
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{
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G4double sign = +1.0; // We always compute a negative number of
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// sigmas. For r > 0 we will multiply by
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// sign = -1 to return a positive number.
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if ( r > .5 ) {
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r = 1-r;
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sign = -1.0;
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}
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G4int index;
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G4double dx;
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if ( r >= Table1step ) {
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index = G4int((Table1size<<1) * r); // 1 to Table1size
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if (index == Table1size) return 0.0;
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dx = (Table1size<<1) * r - index; // fraction of way to next bin
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index += Table1offset-1;
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} else if ( r > Table0step ) {
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G4double rr = r * Table0scale;
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index = G4int(Table0size * rr); // 1 to Table0size
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dx = Table0size * rr - index; // fraction of way to next bin
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index += Table0offset-1;
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} else { // r <= Table0step - not in tables
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return sign*transformSmall(r);
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}
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G4double y0 = gaussTables [index++];
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G4double y1 = gaussTables [index];
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return (G4float) (sign * ( y1 * dx + y0 * (1.0-dx) ));
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} // transformQuick()
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G4double G4MTRandGaussQ::transformSmall (G4double r)
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{
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// Solve for -v in the asymtotic formula
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//
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// errInt (-v) = exp(-v*v/2) 1 1*3 1*3*5
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// ------------ * (1 - ---- + ---- - ----- + ... )
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// v*sqrt(2*pi) v**2 v**4 v**6
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// The value of r (=errInt(-v)) supplied is going to less than 2.0E-13,
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// which is such that v < -7.25. Since the value of r is meaningful only
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// to an absolute error of 1E-16 (double precision accuracy for a number
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// which on the high side could be of the form 1-epsilon), computing
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// v to more than 3-4 digits of accuracy is suspect; however, to ensure
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// smoothness with the table generator (which uses quite a few terms) we
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// also use terms up to 1*3*5* ... *13/v**14, and insist on accuracy of
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// solution at the level of 1.0e-7.
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// This routine is called less than one time in a million firings, so
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// speed is of no concern. As a matter of technique, we terminate the
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// iterations in case they would be infinite, but this should not happen.
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G4double eps = 1.0e-7;
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G4double guess = 7.5;
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G4double v;
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for ( G4int i = 1; i < 50; i++ ) {
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G4double vn2 = 1.0/(guess*guess);
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G4double s = -13*11*9*7*5*3 * vn2*vn2*vn2*vn2*vn2*vn2*vn2;
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s += 11*9*7*5*3 * vn2*vn2*vn2*vn2*vn2*vn2;
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s += -9*7*5*3 * vn2*vn2*vn2*vn2*vn2;
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s += 7*5*3 * vn2*vn2*vn2*vn2;
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s += -5*3 * vn2*vn2*vn2;
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s += 3 * vn2*vn2 - vn2 + 1.0;
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v = std::sqrt ( 2.0 * std::log ( s / (r*guess*std::sqrt(CLHEP::twopi)) ) );
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if ( std::fabs(v-guess) < eps ) break;
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guess = v;
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}
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return -v;
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} // transformSmall()
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#endif
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