EvtCGCoefSingle.cpp

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#include "EvtGenBase/EvtCGCoefSingle.hh"
 
#include "EvtGenBase/EvtOrthogVector.hh"
 
#include <assert.h>
#include <iostream>
#include <math.h>
#include <stdlib.h>
 
void EvtCGCoefSingle::init( int j1, int j2 )
{
    m_j1 = j1;
    m_j2 = j2;
 
    m_Jmax = abs( j1 + j2 );
    m_Jmin = abs( j1 - j2 );
 
    m_table.resize( ( m_Jmax - m_Jmin ) / 2 + 1 );
 
    int J, M;
 
    int lenmax = j1 + 1;
    if ( j2 < j1 )
        lenmax = j2 + 1;
 
    //set vector sizes
    for ( J = m_Jmax; J >= m_Jmin; J -= 2 ) {
        m_table[( J - m_Jmin ) / 2].resize( J + 1 );
        for ( M = J; J >= -M; M -= 2 ) {
            int len = ( ( m_j1 + m_j2 ) - abs( M ) ) / 2 + 1;
            if ( len > lenmax )
                len = lenmax;
            m_table[( J - m_Jmin ) / 2][( M + J ) / 2].resize( len );
        }
    }
 
    //now fill the vectors
    for ( J = m_Jmax; J >= m_Jmin; J -= 2 ) {
        //bootstrap with highest M(=J) as a special case
        if ( J == m_Jmax ) {
            cg( J, J, m_j1, m_j2 ) = 1.0;
        } else {
            int n = ( m_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 = m_table[( m_Jmax - m_Jmin ) / 2 - i]
                                        [( J + m_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++ ) {
                m_table[( J - m_Jmin ) / 2][J][k] = sign * orth[k];
            }
            delete[] vectors;
        }
        for ( M = J - 2; M >= -J; M -= 2 ) {
            int len = ( ( m_j1 + m_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 = m_j1 * ( m_j1 + 2 ) - ( m1 + 2 ) * m1;
                //fkw 2/2/2001: changes needed to satisfy KCC
                //fkw if (m1+2<=m_j1) sum+=0.5*sqrt(m_j1*(m_j1+2)-(m1+2)*m1)*cg(J,M+2,m1+2,m2);
                //fkw if (m2+2<=m_j2) sum+=0.5*sqrt(m_j2*(m_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 <= m_j1 )
                    sum += 0.5 * sqrt( fkwTmp ) * cg( J, M + 2, m1 + 2, m2 );
                fkwTmp = m_j2 * ( m_j2 + 2 ) - ( m2 + 2 ) * m2;
                if ( m2 + 2 <= m_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, [[maybe_unused]] int j1,
                              [[maybe_unused]] int j2, int m1, int m2 )
{
    assert( j1 == m_j1 );
    assert( j2 == m_j2 );
 
    return cg( J, M, m1, m2 );
}
 
double& EvtCGCoefSingle::cg( int J, int M, int m1, [[maybe_unused]] int m2 )
{
    assert( M == m1 + m2 );
    assert( abs( M ) <= J );
    assert( J <= m_Jmax );
    assert( J >= m_Jmin );
    assert( abs( m1 ) <= m_j1 );
    assert( abs( m2 ) <= m_j2 );
 
    //find lowest m1 allowed for the given M
 
    int mmin = M - m_j2;
 
    if ( mmin < -m_j1 )
        mmin = -m_j1;
 
    int n = m1 - mmin;
 
    return m_table[( J - m_Jmin ) / 2][( M + J ) / 2][n / 2];
}