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glibc  2.9
Functions
e_hypot.c File Reference
#include "math.h"
#include "math_private.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 55 of file e_hypot.c.

{
       double a,b,t1,t2,y1,y2,w;
       int32_t j,k,ha,hb;

       GET_HIGH_WORD(ha,x);
       ha &= 0x7fffffff;
       GET_HIGH_WORD(hb,y);
       hb &= 0x7fffffff;
       if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;}
       SET_HIGH_WORD(a,ha); /* a <- |a| */
       SET_HIGH_WORD(b,hb); /* b <- |b| */
       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 */
              u_int32_t low;
              w = a+b;                    /* for sNaN */
              GET_LOW_WORD(low,a);
              if(((ha&0xfffff)|low)==0) w = a;
              GET_LOW_WORD(low,b);
              if(((hb^0x7ff00000)|low)==0) w = b;
              return w;
          }
          /* scale a and b by 2**-600 */
          ha -= 0x25800000; hb -= 0x25800000;    k += 600;
          SET_HIGH_WORD(a,ha);
          SET_HIGH_WORD(b,hb);
       }
       if(hb < 0x20b00000) {       /* b < 2**-500 */
           if(hb <= 0x000fffff) {  /* subnormal b or 0 */
               u_int32_t low;
              GET_LOW_WORD(low,b);
              if((hb|low)==0) return a;
              t1=0;
              SET_HIGH_WORD(t1,0x7fd00000);      /* t1=2^1022 */
              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;
              SET_HIGH_WORD(a,ha);
              SET_HIGH_WORD(b,hb);
           }
       }
    /* medium size a and b */
       w = a-b;
       if (w>b) {
           t1 = 0;
           SET_HIGH_WORD(t1,ha);
           t2 = a-t1;
           w  = __ieee754_sqrt(t1*t1-(b*(-b)-t2*(a+t1)));
       } else {
           a  = a+a;
           y1 = 0;
           SET_HIGH_WORD(y1,hb);
           y2 = b - y1;
           t1 = 0;
           SET_HIGH_WORD(t1,ha+0x00100000);
           t2 = a - t1;
           w  = __ieee754_sqrt(t1*y1-(w*(-w)-(t1*y2+t2*b)));
       }
       if(k!=0) {
           u_int32_t high;
           t1 = 1.0;
           GET_HIGH_WORD(high,t1);
           SET_HIGH_WORD(t1,high+(k<<20));
           return t1*w;
       } else return w;
}

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