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//===========================================================================

//

//      e_rem_pio2.c

//

//      Part of the standard mathematical function library

//

//===========================================================================

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//===========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):   jlarmour

// Contributors:  jlarmour

// Date:        1998-02-13

// Purpose:     

// Description: 

// Usage:       

//

//####DESCRIPTIONEND####

//

//===========================================================================

// CONFIGURATION

#include <pkgconf/libm.h>   // Configuration header

// Include the Math library?

#ifdef CYGPKG_LIBM     

// Derived from code with the following copyright

/* @(#)e_rem_pio2.c 1.4 95/01/18 */

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunSoft, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice

 * is preserved.

 * ====================================================

 *

 */

/* __ieee754_rem_pio2(x,y)

 *

 * return the remainder of x rem pi/2 in y[0]+y[1]

 * use __kernel_rem_pio2()

 */

#include "mathincl/fdlibm.h"

/*

 * Table of constants for 2/pi, 396 Hex digits (476 decimal) of 2/pi

 */

static const int two_over_pi[] = {

0xA2F983, 0x6E4E44, 0x1529FC, 0x2757D1, 0xF534DD, 0xC0DB62,

0x95993C, 0x439041, 0xFE5163, 0xABDEBB, 0xC561B7, 0x246E3A,

0x424DD2, 0xE00649, 0x2EEA09, 0xD1921C, 0xFE1DEB, 0x1CB129,

0xA73EE8, 0x8235F5, 0x2EBB44, 0x84E99C, 0x7026B4, 0x5F7E41,

0x3991D6, 0x398353, 0x39F49C, 0x845F8B, 0xBDF928, 0x3B1FF8,

0x97FFDE, 0x05980F, 0xEF2F11, 0x8B5A0A, 0x6D1F6D, 0x367ECF,

0x27CB09, 0xB74F46, 0x3F669E, 0x5FEA2D, 0x7527BA, 0xC7EBE5,

0xF17B3D, 0x0739F7, 0x8A5292, 0xEA6BFB, 0x5FB11F, 0x8D5D08,

0x560330, 0x46FC7B, 0x6BABF0, 0xCFBC20, 0x9AF436, 0x1DA9E3,

0x91615E, 0xE61B08, 0x659985, 0x5F14A0, 0x68408D, 0xFFD880,

0x4D7327, 0x310606, 0x1556CA, 0x73A8C9, 0x60E27B, 0xC08C6B,

};

static const int npio2_hw[] = {

0x3FF921FB, 0x400921FB, 0x4012D97C, 0x401921FB, 0x401F6A7A, 0x4022D97C,

0x4025FDBB, 0x402921FB, 0x402C463A, 0x402F6A7A, 0x4031475C, 0x4032D97C,

0x40346B9C, 0x4035FDBB, 0x40378FDB, 0x403921FB, 0x403AB41B, 0x403C463A,

0x403DD85A, 0x403F6A7A, 0x40407E4C, 0x4041475C, 0x4042106C, 0x4042D97C,

0x4043A28C, 0x40446B9C, 0x404534AC, 0x4045FDBB, 0x4046C6CB, 0x40478FDB,

0x404858EB, 0x404921FB,

};

/*

 * invpio2:  53 bits of 2/pi

 * pio2_1:   first  33 bit of pi/2

 * pio2_1t:  pi/2 - pio2_1

 * pio2_2:   second 33 bit of pi/2

 * pio2_2t:  pi/2 - (pio2_1+pio2_2)

 * pio2_3:   third  33 bit of pi/2

 * pio2_3t:  pi/2 - (pio2_1+pio2_2+pio2_3)

 */

static const double

zero =  0.00000000000000000000e+00, /* 0x00000000, 0x00000000 */

half =  5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */

two24 =  1.67772160000000000000e+07, /* 0x41700000, 0x00000000 */

invpio2 =  6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */

pio2_1  =  1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */

pio2_1t =  6.07710050650619224932e-11, /* 0x3DD0B461, 0x1A626331 */

pio2_2  =  6.07710050630396597660e-11, /* 0x3DD0B461, 0x1A600000 */

pio2_2t =  2.02226624879595063154e-21, /* 0x3BA3198A, 0x2E037073 */

pio2_3  =  2.02226624871116645580e-21, /* 0x3BA3198A, 0x2E000000 */

pio2_3t =  8.47842766036889956997e-32; /* 0x397B839A, 0x252049C1 */

        int __ieee754_rem_pio2(double x, double *y)

{

        double z,w,t,r,fn;

        double tx[3];

        int e0,i,j,nx,n,ix,hx;

        hx = CYG_LIBM_HI(x);            /* high word of x */

        ix = hx&0x7fffffff;

        if(ix<=0x3fe921fb)   /* |x| ~<= pi/4 , no need for reduction */

            {y[0] = x; y[1] = 0; return 0;}

        if(ix<0x4002d97c) {  /* |x| < 3pi/4, special case with n=+-1 */

            if(hx>0) {

                z = x - pio2_1;

                if(ix!=0x3ff921fb) {    /* 33+53 bit pi is good enough */

                    y[0] = z - pio2_1t;

                    y[1] = (z-y[0])-pio2_1t;

                } else {                /* near pi/2, use 33+33+53 bit pi */

                    z -= pio2_2;

                    y[0] = z - pio2_2t;

                    y[1] = (z-y[0])-pio2_2t;

                }

                return 1;

            } else {    /* negative x */

                z = x + pio2_1;

                if(ix!=0x3ff921fb) {    /* 33+53 bit pi is good enough */

                    y[0] = z + pio2_1t;

                    y[1] = (z-y[0])+pio2_1t;

                } else {                /* near pi/2, use 33+33+53 bit pi */

                    z += pio2_2;

                    y[0] = z + pio2_2t;

                    y[1] = (z-y[0])+pio2_2t;

                }

                return -1;

            }

        }

        if(ix<=0x413921fb) { /* |x| ~<= 2^19*(pi/2), medium size */

            t  = fabs(x);

            n  = (int) (t*invpio2+half);

            fn = (double)n;

            r  = t-fn*pio2_1;

            w  = fn*pio2_1t;    /* 1st round good to 85 bit */

            if(n<32&&ix!=npio2_hw[n-1]) {

                y[0] = r-w;     /* quick check no cancellation */

            } else {

                j  = ix>>20;

                y[0] = r-w;

                i = j-(((CYG_LIBM_HI(y[0]))>>20)&0x7ff);

                if(i>16) {  /* 2nd iteration needed, good to 118 */

                    t  = r;

                    w  = fn*pio2_2;

                    r  = t-w;

                    w  = fn*pio2_2t-((t-r)-w);

                    y[0] = r-w;

                    i = j-(((CYG_LIBM_HI(y[0]))>>20)&0x7ff);

                    if(i>49)  { /* 3rd iteration need, 151 bits acc */

                        t  = r; /* will cover all possible cases */

                        w  = fn*pio2_3;

                        r  = t-w;

                        w  = fn*pio2_3t-((t-r)-w);

                        y[0] = r-w;

                    }

                }

            }

            y[1] = (r-y[0])-w;

            if(hx<0)    {y[0] = -y[0]; y[1] = -y[1]; return -n;}

            else         return n;

        }

    /*

     * all other (large) arguments

     */

        if(ix>=0x7ff00000) {            /* x is inf or NaN */

            y[0]=y[1]=x-x; return 0;

        }

    /* set z = scalbn(|x|,ilogb(x)-23) */

        CYG_LIBM_LO(z) = CYG_LIBM_LO(x);

        e0      = (ix>>20)-1046;        /* e0 = ilogb(z)-23; */

        CYG_LIBM_HI(z) = ix - (e0<<20);

        for(i=0;i<2;i++) {

                tx[i] = (double)((int)(z));

                z     = (z-tx[i])*two24;

        }

        tx[2] = z;

        nx = 3;

        while(tx[nx-1]==zero) nx--;     /* skip zero term */

        n  =  __kernel_rem_pio2(tx,y,e0,nx,2,two_over_pi);

        if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}

        return n;

}

#endif // ifdef CYGPKG_LIBM     

// EOF e_rem_pio2.c