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glibc  2.9
Functions
e_sqrt.c File Reference
#include "endian.h"
#include "mydefs.h"
#include "dla.h"
#include "MathLib.h"
#include "root.tbl"
#include "math_private.h"
#include "uroot.h"
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Functions

double __ieee754_sqrt (double x)

Function Documentation

double __ieee754_sqrt ( double  x)

Definition at line 48 of file e_sqrt.c.

                                {
#include "uroot.h"
  static const double
    rt0 = 9.99999999859990725855365213134618E-01,
    rt1 = 4.99999999495955425917856814202739E-01,
    rt2 = 3.75017500867345182581453026130850E-01,
    rt3 = 3.12523626554518656309172508769531E-01;
  static const double big =  134217728.0;
  double y,t,del,res,res1,hy,z,zz,p,hx,tx,ty,s;
  mynumber a,c={{0,0}};
  int4 k;

  a.x=x;
  k=a.i[HIGH_HALF];
  a.i[HIGH_HALF]=(k&0x001fffff)|0x3fe00000;
  t=inroot[(k&0x001fffff)>>14];
  s=a.x;
  /*----------------- 2^-1022  <= | x |< 2^1024  -----------------*/
  if (k>0x000fffff && k<0x7ff00000) {
    y=1.0-t*(t*s);
    t=t*(rt0+y*(rt1+y*(rt2+y*rt3)));
    c.i[HIGH_HALF]=0x20000000+((k&0x7fe00000)>>1);
    y=t*s;
    hy=(y+big)-big;
    del=0.5*t*((s-hy*hy)-(y-hy)*(y+hy));
    res=y+del;
    if (res == (res+1.002*((y-res)+del))) return res*c.x;
    else {
      res1=res+1.5*((y-res)+del);
      EMULV(res,res1,z,zz,p,hx,tx,hy,ty);  /* (z+zz)=res*res1 */
      return ((((z-s)+zz)<0)?max(res,res1):min(res,res1))*c.x;
    }
  }
  else {
    if ((k & 0x7ff00000) == 0x7ff00000)
      return x*x+x;  /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */
    if (x==0) return x;     /* sqrt(+0)=+0, sqrt(-0)=-0 */
    if (k<0) return (x-x)/(x-x); /* sqrt(-ve)=sNaN */
    return tm256.x*__ieee754_sqrt(x*t512.x);
  }
}