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

Go to the source code of this file.

Functions

double __ieee754_log (double x)

Variables

static double ln2_hi = 6.93147180369123816490e-01
static double ln2_lo = 1.90821492927058770002e-10
static double two54 = 1.80143985094819840000e+16
static double Lg1 = 6.666666666666735130e-01
static double Lg2 = 3.999999999940941908e-01
static double Lg3 = 2.857142874366239149e-01
static double Lg4 = 2.222219843214978396e-01
static double Lg5 = 1.818357216161805012e-01
static double Lg6 = 1.531383769920937332e-01
static double Lg7 = 1.479819860511658591e-01
static double zero = 0.0

Function Documentation

double __ieee754_log ( double  x)

Definition at line 126 of file e_log.c.

{
        fd_twoints u;
       double hfsq,f,s,z,R,w,t1,t2,dk;
       int k,hx,i,j;
       unsigned lx;

        u.d = x;
       hx = __HI(u);        /* high word of x */
       lx = __LO(u);        /* low  word of x */

       k=0;
       if (hx < 0x00100000) {                    /* x < 2**-1022  */
           if (((hx&0x7fffffff)|lx)==0) 
              return -two54/zero;         /* log(+-0)=-inf */
           if (hx<0) return (x-x)/zero;   /* log(-#) = NaN */
           k -= 54; x *= two54; /* subnormal number, scale up x */
            u.d = x;
           hx = __HI(u);           /* high word of x */
       } 
       if (hx >= 0x7ff00000) return x+x;
       k += (hx>>20)-1023;
       hx &= 0x000fffff;
       i = (hx+0x95f64)&0x100000;
        u.d = x;
       __HI(u) = hx|(i^0x3ff00000);       /* normalize x or x/2 */
        x = u.d;
       k += (i>>20);
       f = x-1.0;
       if((0x000fffff&(2+hx))<3) { /* |f| < 2**-20 */
           if(f==zero) { 
                if(k==0) return zero; else {dk=(double)k;
                                            return dk*ln2_hi+dk*ln2_lo;} 
            }
           R = f*f*(0.5-0.33333333333333333*f);
           if(k==0) return f-R; else {dk=(double)k;
                   return dk*ln2_hi-((R-dk*ln2_lo)-f);}
       }
       s = f/(2.0+f); 
       dk = (double)k;
       z = s*s;
       i = hx-0x6147a;
       w = z*z;
       j = 0x6b851-hx;
       t1= w*(Lg2+w*(Lg4+w*Lg6)); 
       t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7))); 
       i |= j;
       R = t2+t1;
       if(i>0) {
           hfsq=0.5*f*f;
           if(k==0) return f-(hfsq-s*(hfsq+R)); else
                   return dk*ln2_hi-((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);
       } else {
           if(k==0) return f-s*(f-R); else
                   return dk*ln2_hi-((s*(f-R)-dk*ln2_lo)-f);
       }
}

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Variable Documentation

double Lg1 = 6.666666666666735130e-01 [static]

Definition at line 113 of file e_log.c.

double Lg2 = 3.999999999940941908e-01 [static]

Definition at line 114 of file e_log.c.

double Lg3 = 2.857142874366239149e-01 [static]

Definition at line 115 of file e_log.c.

double Lg4 = 2.222219843214978396e-01 [static]

Definition at line 116 of file e_log.c.

double Lg5 = 1.818357216161805012e-01 [static]

Definition at line 117 of file e_log.c.

double Lg6 = 1.531383769920937332e-01 [static]

Definition at line 118 of file e_log.c.

double Lg7 = 1.479819860511658591e-01 [static]

Definition at line 119 of file e_log.c.

double ln2_hi = 6.93147180369123816490e-01 [static]

Definition at line 110 of file e_log.c.

double ln2_lo = 1.90821492927058770002e-10 [static]

Definition at line 111 of file e_log.c.

double two54 = 1.80143985094819840000e+16 [static]

Definition at line 112 of file e_log.c.

double zero = 0.0 [static]

Definition at line 121 of file e_log.c.