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lightning-sunbird  0.9+nobinonly
Functions
e_hypot.c File Reference
#include "fdlibm.h"

Go to the source code of this file.

Functions

double __ieee754_hypot (double x, double y)

Function Documentation

double __ieee754_hypot ( double  x,
double  y 
)

Definition at line 89 of file e_hypot.c.

{
        fd_twoints ux, uy;
       double a=x,b=y,t1,t2,y1,y2,w;
       int j,k,ha,hb;
        
        ux.d = x; uy.d = y;
       ha = __HI(ux)&0x7fffffff;   /* high word of  x */
       hb = __HI(uy)&0x7fffffff;   /* high word of  y */
       if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;}
        ux.d = a; uy.d = b;
       __HI(ux) = ha;       /* a <- |a| */
       __HI(uy) = hb;       /* b <- |b| */
        a = ux.d; b = uy.d;
       if((ha-hb)>0x3c00000) {return a+b;} /* x/y > 2**60 */
       k=0;
       if(ha > 0x5f300000) {       /* a>2**500 */
          if(ha >= 0x7ff00000) {   /* Inf or NaN */
              w = a+b;                    /* for sNaN */
               ux.d = a; uy.d = b;
              if(((ha&0xfffff)|__LO(ux))==0) w = a;
              if(((hb^0x7ff00000)|__LO(uy))==0) w = b;
              return w;
          }
          /* scale a and b by 2**-600 */
          ha -= 0x25800000; hb -= 0x25800000;    k += 600;
           ux.d = a; uy.d = b;
          __HI(ux) = ha;
          __HI(uy) = hb;
           a = ux.d; b = uy.d;
       }
       if(hb < 0x20b00000) {       /* b < 2**-500 */
           if(hb <= 0x000fffff) {  /* subnormal b or 0 */      
                uy.d = b;
              if((hb|(__LO(uy)))==0) return a;
              t1=0;
                ux.d = t1;
              __HI(ux) = 0x7fd00000;      /* t1=2^1022 */
                t1 = ux.d;
              b *= t1;
              a *= t1;
              k -= 1022;
           } else {         /* scale a and b by 2^600 */
               ha += 0x25800000;   /* a *= 2^600 */
              hb += 0x25800000;    /* b *= 2^600 */
              k -= 600;
                ux.d = a; uy.d = b;
              __HI(ux) = ha;
              __HI(uy) = hb;
                a = ux.d; b = uy.d;
           }
       }
    /* medium size a and b */
       w = a-b;
       if (w>b) {
           t1 = 0;
            ux.d = t1;
           __HI(ux) = ha;
            t1 = ux.d;
           t2 = a-t1;
           w  = fd_sqrt(t1*t1-(b*(-b)-t2*(a+t1)));
       } else {
           a  = a+a;
           y1 = 0;
            ux.d = y1;
           __HI(ux) = hb;
            y1 = ux.d;
           y2 = b - y1;
           t1 = 0;
            ux.d = t1;
           __HI(ux) = ha+0x00100000;
            t1 = ux.d;
           t2 = a - t1;
           w  = fd_sqrt(t1*y1-(w*(-w)-(t1*y2+t2*b)));
       }
       if(k!=0) {
           t1 = 1.0;
            ux.d = t1;
           __HI(ux) += (k<<20);
            t1 = ux.d;
           return t1*w;
       } else return w;
}

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