/*  sdcbse.cpp  by K.Tsuru  */
// function ID = 3554  DRADIX

/***********************************************************************************************
Basic file for computation of e=2.7181... with Xavier Gourdon's
binary splitting method.
CPU time = 23.5017(sec) 10000029(10 million digits) gcc 4.8.1 + CPU Core i7-3770 3.4GHz
[reference]
e.c in
http://xavier.gourdon.free.fr/Constants/constants.html
The implement is almost the same.

Xavier Gourdon's binary splitting method is based on the original work of
E.A.Karatsuba, "Fast evaluation of hypergeometric functions by FEE", CMFT'97.
See "Binary splitting method" in http://numbers.computation.free.fr/Constants/constants.html .
************************************************************************************************/

#ifndef SN_H
#include "sn.h"
#endif
/********************
In snum.h

#define SLONG 2
#define SDOUBLE 3
#define SDEC_INT 4

are defined.

Speed test for 524,252 digits on Pentium 4 3GHz.

version | CPU time (sec.)
---------------------
SLONG   | 6.2 ... fastest
SDOUBLE | 9.3
SDEC_INT| 9.65
********************/
////////////////////
#define BSE_TYPE SLONG  // for speed test change here
///////////////////

#if BSE_TYPE==SLONG

/// SLong version ///

class BSExp1 : public BinarySplittingA1C<SLong> {
public:
    BSExp1(long L, long prec) : BinarySplittingA1C<SLong>(L, prec) {}

    void setAC(long k, SLong& a, SLong& c) {
        a.SetSmall(1);  c.SetLong(k + 1L);
    }

    SDouble getValue() {
        putTogether();
        return BinarySplittingA1C<SLong>::getValue() + 1.0;
    }
};
#elif BSE_TYPE==SDEC_INT

/// SInteger version ///

class BSExp1 : public BinarySplittingA1C<SInteger> {
public:
    BSExp1(long L, long prec) : BinarySplittingA1C<SInteger>(L, prec) {}

    void setAC(long k, SInteger& a, SInteger& c) {
        a.SetSmall(1);  c.SetLong(k + 1L);
    }

    SDouble getValue() {
        putTogether();
        SLong a , c;
        a = getA().ConvToDec();
        c = getC().ConvToDec();
        return SDouble(a) / SDouble(c) + 1.0;
    }
};
#else
/// SDouble version ///
class BSExp1 : public BinarySplittingA1C<SDouble> {
public:
    BSExp1(long L, long prec) : BinarySplittingA1C<SDouble>(L, prec) {}

    void setAC(long k, SDouble& a, SDouble& c) {
        a.SetSmall(1);
        //c = k + 1L;
        c.SetInt(k + 1L);
    }

    SDouble getValue() {
        putTogether();
        return BinarySplittingA1C<SDouble>::getValue() + 1.0;
    }
};

#endif

SDouble BSE() {
    SDouble temp;
    long prec = long(temp.EffFig() + temp.Hidden()) * DFIGURES;
    long L = upToExpSeries(prec, 0.0);

#if BSE_TYPE==SDOUBLE
    BSExp1 e(L, 0); // does not need roundoff
#else
    BSExp1 e(L, prec);
#endif  
    return e.getValue();
}