ExtendedMath.cc

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//Copyright (c) 2013-2014, The MercuryDPM Developers Team. All rights reserved.
//For the list of developers, see <http://www.MercuryDPM.org/Team>.
//
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//  * Redistributions in binary form must reproduce the above copyright
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//    derived from this software without specific prior written permission.
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#include "ExtendedMath.h"

#include <cmath>
#include <assert.h>
//#include <limits>
//#include <iostream>
//#include <sys/stat.h>
#include <iomanip>
//#include <cmath>
//#include <sstream>
//#include <cstdlib>
//#include <limits>
//#include <string>

Mdouble mathsFunc::gamma(Mdouble gamma_in)
{
    const Mdouble ep = 1e-5;
    
    if (gamma_in > 1.0 + ep)
    {
        return ((gamma_in - 1) * gamma(gamma_in - 1));
    }
    else
    {
        
        if ((gamma_in - ep < 1.0) && (gamma_in + ep > 1.0))
            return 1.0;
        else if ((gamma_in - ep < 0.5) && (gamma_in + ep > 0.5))
            return constants::sqrt_pi;
        else
            return std::numeric_limits<Mdouble>::quiet_NaN();
    }
} //end func gamma

Mdouble mathsFunc::chi_squared(const Mdouble x, const unsigned int k)
{
    
    Mdouble prefactor = pow(2, k / 2.0) * gamma(k / 2.0);
    Mdouble mainfactor = pow(x, k / 2.0 - 1) * exp(x / -2.0);
    
    return mainfactor / prefactor;
    
}

Mdouble mathsFunc::chi_squared_prob(const Mdouble x_max, const unsigned int k)
{
    
//The current value was picked by tried were it stopped effect the 4 d.p.
    const int num_steps_per_unit = 100;
    Mdouble sum = 0;
    Mdouble x = 0;
    long int num_steps = static_cast<int>(num_steps_per_unit * x_max);
//Use trapezional rule, but ignoring the ends
    for (int i = 0; i < num_steps; i++)
    {
        x = x_max / num_steps * (i + 0.5);
        sum = sum + chi_squared(x, k);
    }
    return 1.0 - sum * x_max / num_steps;
    
}

Mdouble mathsFunc::goldenSectionSearch(Mdouble(*function)(const Mdouble), Mdouble min, Mdouble cur, Mdouble max, Mdouble endCondition, Mdouble curVal)
{
    if (std::abs(max - min) < endCondition)
    {
        return 0.5 * (min + max);
    }
    std::cout << "Min=" << min << " Max=" << max << " diff=" << max - min << std::endl;
    double resphi = 2 - 0.5 * (1 + std::sqrt(5));
    double x;
    if (max - cur > cur - min)
    {
        x = cur + resphi * (max - cur);
    }
    else
    {
        x = cur - resphi * (cur - min);
    }
    if(std::isnan(curVal))
        curVal = function(cur);
    double xVal = function(x);
    if (xVal < curVal)
    {
        if (max - cur > cur - min)
        {
            return goldenSectionSearch(function, cur, x, max, endCondition, xVal);
        }
        else
        {
            return goldenSectionSearch(function, min, x, cur, endCondition, xVal);
        }
    }
    else
    {
        if (max - cur > cur - min)
        {
            return goldenSectionSearch(function, min, cur, x, endCondition, curVal);
        }
        else
        {
            return goldenSectionSearch(function, x, cur, max, endCondition, curVal);
        }
    }
}

bool mathsFunc::isEqual(Mdouble v1, Mdouble v2, double absError)
{
    return std::abs(v1 - v2) <= absError;
}


bool mathsFunc::isEqual(Vec3D v1, Vec3D v2, double absError)
{
    return isEqual(v1.X,v2.X,absError)&&isEqual(v1.Y,v2.Y,absError)&&isEqual(v1.Z,v2.Z,absError);
}

Mdouble besselFunc::chebyshev(Mdouble x, const Mdouble coef[], int N)
{
    const Mdouble *p = coef;
    Mdouble b0 = *p++;
    Mdouble b1 = 0, b2;
    int i = N - 1;
    
    assert(i > 0);
    do
    {
        b2 = b1;
        b1 = b0;
        b0 = x * b1 - b2 + *p++;
    }
    while ( --i);
    
    return (0.5 * (b0 - b2));
}

Mdouble besselFunc::I0_exp(Mdouble x)
{
    // Cooefficients for [0..8]
    const Mdouble A[] =
            {
                    -4.415341646479339379501E-18,
                    3.330794518822238097831E-17,
                    -2.431279846547954693591E-16,
                    1.715391285555133030611E-15,
                    -1.168533287799345168081E-14,
                    7.676185498604935616881E-14,
                    -4.856446783111929460901E-13,
                    2.955052663129639834611E-12,
                    -1.726826291441555707231E-11,
                    9.675809035373236912241E-11,
                    -5.189795601635262906661E-10,
                    2.659823724682386650351E-9,
                    -1.300025009986248042121E-8,
                    6.046995022541918949321E-8,
                    -2.670793853940611733911E-7,
                    1.117387539120103718151E-6,
                    -4.416738358458750563591E-6,
                    1.644844807072889708931E-5,
                    -5.754195010082103703981E-5,
                    1.885028850958416557291E-4,
                    -5.763755745385823658851E-4,
                    1.639475616941335798421E-3,
                    -4.324309995050575944301E-3,
                    1.054646039459499831831E-2,
                    -2.373741480589946881561E-2,
                    4.930528423967070848781E-2,
                    -9.490109704804764442101E-2,
                    1.716209015222087753491E-1,
                    -3.046826723431983986831E-1,
                    6.767952744094760849951E-1
            };
    
    // Cooefficients for [8..infinity]
    const Mdouble B[] =
            {
                    -7.233180487874753954561E-18,
                    -4.830504485944182071261E-18,
                    4.465621420296759999011E-17,
                    3.461222867697461093101E-17,
                    -2.827623980516583484941E-16,
                    -3.425485619677219134621E-16,
                    1.772560133056526383601E-15,
                    3.811680669352622420751E-15,
                    -9.554846698828307648701E-15,
                    -4.150569347287222086631E-14,
                    1.540086217521409826911E-14,
                    3.852778382742142701141E-13,
                    7.180124451383666233671E-13,
                    -1.794178531506806117781E-12,
                    -1.321581184044771311881E-11,
                    -3.149916527963241364541E-11,
                    1.188914710784643834241E-11,
                    4.940602388224969589101E-10,
                    3.396232025708386345151E-9,
                    2.266668990498178064591E-8,
                    2.048918589469063741831E-7,
                    2.891370520834756482971E-6,
                    6.889758346916823984261E-5,
                    3.369116478255694089901E-3,
                    8.044904110141088316081E-1
            };
    
    if (x < 0)
        x = -x;
    
    if (x <= 8.0)
    {
        Mdouble y = (x / 2.0) - 2.0;
        return (chebyshev(y, A, 30));
    }
    
    return (chebyshev(32.0 / x - 2.0, B, 25) / sqrt(x));
}

Mdouble besselFunc::I0(Mdouble x)
{
    if (x < 0)
        x = -x;
    return exp(x) * I0_exp(x);
}