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EvtCGCoefSingle.cpp
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EvtCGCoefSingle.cpp
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/***********************************************************************
* Copyright 1998-2020 CERN for the benefit of the EvtGen authors *
* *
* This file is part of EvtGen. *
* *
* EvtGen is free software: you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation, either version 3 of the License, or *
* (at your option) any later version. *
* *
* EvtGen is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with EvtGen. If not, see <https://www.gnu.org/licenses/>. *
***********************************************************************/
#include "EvtGenBase/EvtCGCoefSingle.hh"
#include "EvtGenBase/EvtOrthogVector.hh"
#include "EvtGenBase/EvtPatches.hh"
#include <assert.h>
#include <iostream>
#include <math.h>
#include <stdlib.h>
void EvtCGCoefSingle::init( int j1, int j2 )
{
_j1 = j1;
_j2 = j2;
_Jmax = abs( j1 + j2 );
_Jmin = abs( j1 - j2 );
_table.resize( ( _Jmax - _Jmin ) / 2 + 1 );
int J, M;
int lenmax = j1 + 1;
if ( j2 < j1 )
lenmax = j2 + 1;
//set vector sizes
for ( J = _Jmax; J >= _Jmin; J -= 2 ) {
_table[( J - _Jmin ) / 2].resize( J + 1 );
for ( M = J; J >= -M; M -= 2 ) {
int len = ( ( _j1 + _j2 ) - abs( M ) ) / 2 + 1;
if ( len > lenmax )
len = lenmax;
_table[( J - _Jmin ) / 2][( M + J ) / 2].resize( len );
}
}
//now fill the vectors
for ( J = _Jmax; J >= _Jmin; J -= 2 ) {
//bootstrap with highest M(=J) as a special case
if ( J == _Jmax ) {
cg( J, J, _j1, _j2 ) = 1.0;
} else {
int n = ( _Jmax - J ) / 2 + 1;
std::vector<double>* vectors = new std::vector<double>[n - 1];
int i, k;
for ( i = 0; i < n - 1; i++ ) {
// i corresponds to J=Jmax-2*i
vectors[i].resize( n );
for ( k = 0; k < n; k++ ) {
double tmp = _table[( _Jmax - _Jmin ) / 2 - i]
[( J + _Jmax - 2 * i ) / 2][k];
vectors[i][k] = tmp;
}
}
EvtOrthogVector getOrth( n, vectors );
std::vector<double> orth = getOrth.getOrthogVector();
int sign = 1;
if ( orth[n - 1] < 0.0 )
sign = -1;
for ( k = 0; k < n; k++ ) {
_table[( J - _Jmin ) / 2][J][k] = sign * orth[k];
}
delete[] vectors;
}
for ( M = J - 2; M >= -J; M -= 2 ) {
int len = ( ( _j1 + _j2 ) - abs( M ) ) / 2 + 1;
if ( len > lenmax )
len = lenmax;
int mmin = M - j2;
if ( mmin < -j1 )
mmin = -j1;
int m1;
for ( m1 = mmin; m1 < mmin + len * 2; m1 += 2 ) {
int m2 = M - m1;
double sum = 0.0;
float fkwTmp = _j1 * ( _j1 + 2 ) - ( m1 + 2 ) * m1;
//fkw 2/2/2001: changes needed to satisfy KCC
//fkw if (m1+2<=_j1) sum+=0.5*sqrt(_j1*(_j1+2)-(m1+2)*m1)*cg(J,M+2,m1+2,m2);
//fkw if (m2+2<=_j2) sum+=0.5*sqrt(_j2*(_j2+2)-(m2+2)*m2)*cg(J,M+2,m1,m2+2);
//fkw sum/=(0.5*sqrt(J*(J+2)-(M+2)*M));
if ( m1 + 2 <= _j1 )
sum += 0.5 * sqrt( fkwTmp ) * cg( J, M + 2, m1 + 2, m2 );
fkwTmp = _j2 * ( _j2 + 2 ) - ( m2 + 2 ) * m2;
if ( m2 + 2 <= _j2 )
sum += 0.5 * sqrt( fkwTmp ) * cg( J, M + 2, m1, m2 + 2 );
fkwTmp = J * ( J + 2 ) - ( M + 2 ) * M;
sum /= ( 0.5 * sqrt( fkwTmp ) );
cg( J, M, m1, m2 ) = sum;
}
}
}
}
double EvtCGCoefSingle::coef( int J, int M, int j1, int j2, int m1, int m2 )
{
assert( j1 == _j1 );
_unused( j1 );
assert( j2 == _j2 );
_unused( j2 );
return cg( J, M, m1, m2 );
}
double& EvtCGCoefSingle::cg( int J, int M, int m1, int m2 )
{
assert( M == m1 + m2 );
_unused( m2 );
assert( abs( M ) <= J );
assert( J <= _Jmax );
assert( J >= _Jmin );
assert( abs( m1 ) <= _j1 );
assert( abs( m2 ) <= _j2 );
//find lowest m1 allowed for the given M
int mmin = M - _j2;
if ( mmin < -_j1 )
mmin = -_j1;
int n = m1 - mmin;
return _table[( J - _Jmin ) / 2][( M + J ) / 2][n / 2];
}

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