simpnumer.h

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#pragma once

/*
________________________________________________________________________

 (C) dGB Beheer B.V.; (LICENSE) http://opendtect.org/OpendTect_license.txt
 Author:        Bert Bril & Kris Tingdahl
 Date:          12-4-1999
 Contents:      'Simple' numerical functions
________________________________________________________________________

*/

#include "algomod.h"
#include "typeset.h"
#include "undefval.h"
#include "ranges.h"
#include "math2.h"


namespace Interpolate
{

inline int getArrIdxPosition( const float farridx, const int arrsz,
                              float& relpos, const float eps=1e-4 )
{
    int arridx = (int)farridx;
    relpos = farridx - arridx;

    if ( arridx==-1 && mIsEqual(relpos,1,1e-4) )
        { arridx = 0; relpos = 0; }
    else if ( arridx==arrsz-1 && mIsZero(relpos,1e-4) )
        { arridx = arrsz-2; relpos = 1; }

    return arridx;
}

} // namespace Interpolate


template <class T> inline
T greatestCommonDivisor( T val0, T val1 )
{
    T shift = 0;

    if ( !val0 ) return val1;
    if ( !val1 ) return val0;

    while ( (val0&1)==0  &&  (val1&1)==0 )
    {
        val0 >>= 1;
        val1 >>= 1;
        shift++;
    }

    do
    {
        if ((val0 & 1) == 0)
            val0 >>= 1;
        else if ((val1 & 1) == 0)
            val1 >>= 1;
        else if (val0 >= val1)
            val0 = (val0-val1) >> 1;
        else
            val1 = (val1-val0) >> 1;
    } while ( val0 );

    return val1 << shift;
}


template <class T> inline
StepInterval<T> getCommonStepInterval( const StepInterval<T>& a,
                                        const StepInterval<T>& b )
{
    const T start = mMIN( a.start, b.start );

    T step = greatestCommonDivisor( a.step, b.step );
    step = greatestCommonDivisor( step, (T) Math::Abs(a.start-b.start) );

    const T stop = mMAX( a.start+((T)a.nrSteps())*a.step,
                         b.start+((T)b.nrSteps())*b.step );
    return StepInterval<T>( start, stop, step );
}


template <class iT>
inline iT exactPower( iT val, iT base )
{
    if ( val==base ) return 1;

    if ( val%base )
        return 0;

    iT res = exactPower( val/base, base );
    if ( res ) return 1 + res;

    return 0;
}


template <class iT>
inline iT nextPower( iT val, iT base )
{
    iT res = 1;
    while ( res<val ) res *= base;
    return res;
}


template <class iT>
inline iT getPow2Sz( iT actsz, const bool above=true,
                     iT minsz=1, iT maxsz=0 )
{
    char npow = 0; char npowextra = actsz == 1 ? 1 : 0;
    iT sz = actsz;
    while ( sz>1 )
    {
        if ( above && !npowextra && sz % 2 )
            npowextra = 1;
        sz /= 2; npow++;
    }

    sz = Math::IntPowerOf( 2, npow + npowextra );
    if ( sz<minsz ) sz = minsz;
    if ( maxsz && sz>maxsz ) sz = maxsz;
    return sz;
}


template <class iT>
inline iT nextPower2( iT nr, iT minnr, iT maxnr )
{
    if ( nr>maxnr )
        return maxnr;

    iT newnr = minnr;
    while ( nr > newnr )
        newnr *= 2;

    return newnr;
}


template <class iT>
inline iT nrBlocks( iT totalsamples, iT basesize, iT overlapsize )
{
    iT res = 0;
    while ( totalsamples>basesize )
    {
        res++;
        totalsamples = totalsamples - basesize + overlapsize;
    }

    return res+1;
}


namespace Taper
{
    enum Type { Cosine, Linear };
};


template <class T>
bool taperArray( T* array, int sz, int lowpos, int highpos, Taper::Type type )
{
    if ( lowpos  >= sz || lowpos  < 0 ||
         highpos >= sz || highpos < 0 ||
         highpos == lowpos )
        return false;

    int pos = lowpos < highpos ? 0 : sz - 1 ;
    int inc = lowpos < highpos ? 1 : -1 ;

    while ( pos != lowpos )
    {
        array[pos] = 0;
        pos += inc;
    }

    int tapersz = abs( highpos - lowpos );
    float taperfactor = type == Taper::Cosine ? M_PI : 0;
    float taperfactorinc = ( type == Taper::Cosine ? M_PI : 1 ) / tapersz;


    while ( pos != highpos )
    {
        array[pos] *= type == Taper::Cosine ? .5 + .5 * cos( taperfactor )
                                            : taperfactor;
        pos += inc;
        taperfactor += taperfactorinc;
    }

    return true;
}


template <class T>
inline T sampledGradient( T ym2, T ym1, T y0_, T y1_, T y2 )
{
    bool um1 = Values::isUdf(ym1), u0 = Values::isUdf(y0_),
                u1 = Values::isUdf(y1_);

    if ( Values::isUdf(ym2) || Values::isUdf(y2) )
    {
        if ( um1 || u1 )
            { if ( !u0 && !(um1 && u1) ) return um1 ? y1_ - y0_ : y0_ - ym1; }
        else
            return (y1_-ym1) * .5;
    }
    else if ( (um1 && u1) || (u0 && (um1 || u1)) )
        return (y2-ym2) * .25;
    else if ( um1 || u1 )
    {
        return um1 ? ((16*y1_)   - 3*y2  - ym2) / 12 - y0_
                   : ((-16*ym1) + 3*ym2 + y2)  / 12 + y0_;
    }
    else
        return (8 * ( y1_ - ym1 ) - y2 + ym2) / 12;

    return mUdf(T);
}


template <class X, class Y, class RT>
inline void getGradient( const X& x, const Y& y, int sz, int firstx, int firsty,
                  RT* gradptr=0, RT* interceptptr=0 )
{
    RT xy_sum = 0, x_sum=0, y_sum=0, xx_sum=0;

    for ( int idx=0; idx<sz; idx++ )
    {
        RT xval = x[idx+firstx];
        RT yval = y[idx+firsty];

        x_sum += xval;
        y_sum += yval;
        xx_sum += xval*xval;
        xy_sum += xval*yval;
    }

    RT grad = ( sz*xy_sum - x_sum*y_sum ) / ( sz*xx_sum - x_sum*x_sum );
    if ( gradptr ) *gradptr = grad;

    if ( interceptptr ) *interceptptr = (y_sum - grad*x_sum)/sz;
}


template <class X>
inline float variance( const X& x, int sz )
{
    if ( sz < 2 ) return mUdf(float);

    float sum=0;
    float sqsum=0;

    for ( int idx=0; idx<sz; idx++ )
    {
        float val = x[idx];

        sum += val;
        sqsum += val*val;
    }

    return (sqsum - sum * sum / sz)/ (sz -1);
}


inline int solve3DPoly( double a, double b, double c,
                         double& root0,
                         double& root1,
                         double& root2 )
{
    const double a2 = a*a;
    const double q = (a2-3*b)/9;
    const double r = (2*a2*a-9*a*b+27*c)/54;
    const double q3 = q*q*q;
    const double r2 = r*r;


    const double minus_a_through_3 = -a/3;

    if ( r2<q3 )
    {
        const double minus_twosqrt_q = -2*Math::Sqrt(q);
        const double theta = Math::ACos(r/Math::Sqrt(q3));
        const double twopi = M_2PI;


        root0 = minus_twosqrt_q*cos(theta/3)+minus_a_through_3;
        root1=minus_twosqrt_q*cos((theta-twopi)/3)+minus_a_through_3;
        root2=minus_twosqrt_q*cos((theta+twopi)/3)+minus_a_through_3;
        return 3;
    }

    const double A=(r>0?-1:1)*pow(fabs(r)+Math::Sqrt(r2-q3),1/3);
    const double B=mIsZero(A,mDefEps)?0:q/A;

    root0 = A+B+minus_a_through_3;

    return 1;
}


template <class T>
inline bool holdsClassValue( const T val, const unsigned int maxclss=50 )
{
    if ( mIsUdf(val) ) return true;
    if ( val < -mDefEps ) return false;
    const int ival = (int)(val + .5);
    return ival <= maxclss && mIsEqual(val,ival,mDefEps);
}


template <class T>
inline bool holdsClassValues( const T* vals, od_int64 sz,
                              const unsigned int maxclss=50,
                              const unsigned int samplesz=100 )
{
    if ( sz < 1 ) return true;
    if ( sz <= samplesz )
    {
        for ( int idx=0; idx<sz; idx++ )
        {
            if ( !holdsClassValue(vals[idx],maxclss) )
                return false;
        }
        return true;
    }

    mDefineStaticLocalObject( od_int64, seed, = mUdf(od_int64) );
    seed *= seed + 1; // Clumsy but cheap sort-of random generation

    for ( int idx=0; idx<samplesz; idx++ )
    {
        od_int64 arridx = ((1+idx) * seed) % samplesz;
        if ( arridx<0 )
            arridx = -arridx;

        if ( !holdsClassValue(vals[arridx],maxclss) )
            return false;
    }
    return true;
}


template <class T>
inline bool isSigned8BitesValue( const T val )
{
    if ( val>127 || val<-128 )
        return false;

    const int ival = (int)(val>0 ? val+.5 : val-.5);
    return mIsEqual(val,ival,mDefEps);
}


template <class T>
inline bool is8BitesData( const T* vals, od_int64 sz,
        const unsigned int samplesz=100 )
{
    if ( holdsClassValues(vals,sz,255,samplesz) )
        return true;

    if ( sz <= samplesz )
    {
        for ( int idx=0; idx<sz; idx++ )
        {
            if ( !isSigned8BitesValue(vals[idx]) )
                return false;
        }
        return true;
    }

    mDefineStaticLocalObject( od_int64, seed, = mUdf(od_int64) );
    seed *= seed + 1; // Clumsy but cheap sort-of random generation

    for ( int idx=0; idx<samplesz; idx++ )
    {
        od_int64 arridx = ((1+idx) * seed) % samplesz;
        if ( arridx<0 )
            arridx = -arridx;

        if ( !isSigned8BitesValue(vals[arridx]) )
            return false;
    }
    return true;
}