sysdeps/ieee754/dbl-64/branred.c

   1 /*
   2  * IBM Accurate Mathematical Library
   3  * Written by International Business Machines Corp.
   4  * Copyright (C) 2001, 2011 Free Software Foundation, Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19 /*******************************************************************/
  20 /*                                                                 */
  21 /* MODULE_NAME: branred.c                                          */
  22 /*                                                                 */
  23 /* FUNCTIONS:   branred                                            */
  24 /*                                                                 */
  25 /* FILES NEEDED: branred.h mydefs.h endian.h mpa.h                 */
  26 /*               mha.c                                             */
  27 /*                                                                 */
  28 /* Routine  branred() performs range  reduction of a double number */
  29 /* x into Double length number  a+aa,such that                     */
  30 /* x=n*pi/2+(a+aa), abs(a+aa)<pi/4, n=0,+-1,+-2,....               */
  31 /* Routine returns the integer (n mod 4) of the above description  */
  32 /* of x.                                                           */
  33 /*******************************************************************/
  34
  35 #include "endian.h"
  36 #include "mydefs.h"
  37 #include "branred.h"
  38 #include <math_private.h>
  39
  40 #ifndef SECTION
  41 # define SECTION
  42 #endif
  43
  44
  45 /*******************************************************************/
  46 /* Routine  branred() performs range  reduction of a double number */
  47 /* x into Double length number a+aa,such that                      */
  48 /* x=n*pi/2+(a+aa), abs(a+aa)<pi/4, n=0,+-1,+-2,....               */
  49 /* Routine return integer (n mod 4)                                */
  50 /*******************************************************************/
  51 int
  52 SECTION
  53 __branred(double x, double *a, double *aa)
  54 {
  55   int i,k;
  56 #if 0
  57   int n;
  58 #endif
  59   mynumber  u,gor;
  60 #if 0
  61   mynumber v;
  62 #endif
  63   double r[6],s,t,sum,b,bb,sum1,sum2,b1,bb1,b2,bb2,x1,x2,t1,t2;
  64
  65   x*=tm600.x;
  66   t=x*split;   /* split x to two numbers */
  67   x1=t-(t-x);
  68   x2=x-x1;
  69   sum=0;
  70   u.x = x1;
  71   k = (u.i[HIGH_HALF]>>20)&2047;
  72   k = (k-450)/24;
  73   if (k<0)
  74     k=0;
  75   gor.x = t576.x;
  76   gor.i[HIGH_HALF] -= ((k*24)<<20);
  77   for (i=0;i<6;i++)
  78     { r[i] = x1*toverp[k+i]*gor.x; gor.x *= tm24.x; }
  79   for (i=0;i<3;i++) {
  80     s=(r[i]+big.x)-big.x;
  81     sum+=s;
  82     r[i]-=s;
  83   }
  84   t=0;
  85   for (i=0;i<6;i++)
  86     t+=r[5-i];
  87   bb=(((((r[0]-t)+r[1])+r[2])+r[3])+r[4])+r[5];
  88   s=(t+big.x)-big.x;
  89   sum+=s;
  90   t-=s;
  91   b=t+bb;
  92   bb=(t-b)+bb;
  93   s=(sum+big1.x)-big1.x;
  94   sum-=s;
  95   b1=b;
  96   bb1=bb;
  97   sum1=sum;
  98   sum=0;
  99
 100   u.x = x2;
 101   k = (u.i[HIGH_HALF]>>20)&2047;
 102   k = (k-450)/24;
 103   if (k<0)
 104     k=0;
 105   gor.x = t576.x;
 106   gor.i[HIGH_HALF] -= ((k*24)<<20);
 107   for (i=0;i<6;i++)
 108     { r[i] = x2*toverp[k+i]*gor.x; gor.x *= tm24.x; }
 109   for (i=0;i<3;i++) {
 110     s=(r[i]+big.x)-big.x;
 111     sum+=s;
 112     r[i]-=s;
 113   }
 114   t=0;
 115   for (i=0;i<6;i++)
 116     t+=r[5-i];
 117   bb=(((((r[0]-t)+r[1])+r[2])+r[3])+r[4])+r[5];
 118   s=(t+big.x)-big.x;
 119  sum+=s;
 120  t-=s;
 121  b=t+bb;
 122  bb=(t-b)+bb;
 123  s=(sum+big1.x)-big1.x;
 124  sum-=s;
 125
 126  b2=b;
 127  bb2=bb;
 128  sum2=sum;
 129
 130  sum=sum1+sum2;
 131  b=b1+b2;
 132  bb = (ABS(b1)>ABS(b2))? (b1-b)+b2 : (b2-b)+b1;
 133  if (b > 0.5)
 134    {b-=1.0; sum+=1.0;}
 135  else if (b < -0.5)
 136    {b+=1.0; sum-=1.0;}
 137  s=b+(bb+bb1+bb2);
 138  t=((b-s)+bb)+(bb1+bb2);
 139  b=s*split;
 140  t1=b-(b-s);
 141  t2=s-t1;
 142  b=s*hp0.x;
 143  bb=(((t1*mp1.x-b)+t1*mp2.x)+t2*mp1.x)+(t2*mp2.x+s*hp1.x+t*hp0.x);
 144  s=b+bb;
 145  t=(b-s)+bb;
 146  *a=s;
 147  *aa=t;
 148  return ((int) sum)&3; /* return quater of unit circle */
 149 }