Back to index

lightning-sunbird  0.9+nobinonly
Functions | Variables
s_log1p.c File Reference
#include "fdlibm.h"

Go to the source code of this file.

Functions

double fd_log1p (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 Lp1 = 6.666666666666735130e-01
static double Lp2 = 3.999999999940941908e-01
static double Lp3 = 2.857142874366239149e-01
static double Lp4 = 2.222219843214978396e-01
static double Lp5 = 1.818357216161805012e-01
static double Lp6 = 1.531383769920937332e-01
static double Lp7 = 1.479819860511658591e-01
static double zero = 0.0

Function Documentation

double fd_log1p ( double  x)

Definition at line 140 of file s_log1p.c.

{
       double hfsq,f,c,s,z,R,u;
       int k,hx,hu,ax;
        fd_twoints un;

        un.d = x;
       hx = __HI(un);              /* high word of x */
       ax = hx&0x7fffffff;

       k = 1;
       if (hx < 0x3FDA827A) {                    /* x < 0.41422  */
           if(ax>=0x3ff00000) {           /* x <= -1.0 */
              if(x==-1.0) return -two54/zero; /* log1p(-1)=+inf */
              else return (x-x)/(x-x);    /* log1p(x<-1)=NaN */
           }
           if(ax<0x3e200000) {                   /* |x| < 2**-29 */
              if(two54+x>zero                    /* raise inexact */
                   &&ax<0x3c900000)              /* |x| < 2**-54 */
                  return x;
              else
                  return x - x*x*0.5;
           }
           if(hx>0||hx<=((int)0xbfd2bec3)) {
              k=0;f=x;hu=1;}       /* -0.2929<x<0.41422 */
       } 
       if (hx >= 0x7ff00000) return x+x;
       if(k!=0) {
           if(hx<0x43400000) {
              u  = 1.0+x; 
                un.d = u;
               hu = __HI(un);             /* high word of u */
               k  = (hu>>20)-1023;
               c  = (k>0)? 1.0-(u-x):x-(u-1.0);/* correction term */
              c /= u;
           } else {
              u  = x;
                un.d = u;
               hu = __HI(un);             /* high word of u */
               k  = (hu>>20)-1023;
              c  = 0;
           }
           hu &= 0x000fffff;
           if(hu<0x6a09e) {
                un.d = u;
               __HI(un) = hu|0x3ff00000;  /* normalize u */
                u = un.d;
           } else {
               k += 1; 
                un.d = u;
               __HI(un) = hu|0x3fe00000;  /* normalize u/2 */
                u = un.d;
               hu = (0x00100000-hu)>>2;
           }
           f = u-1.0;
       }
       hfsq=0.5*f*f;
       if(hu==0) {   /* |f| < 2**-20 */
           if(f==zero) if(k==0) return zero;  
                     else {c += k*ln2_lo; return k*ln2_hi+c;}
           R = hfsq*(1.0-0.66666666666666666*f);
           if(k==0) return f-R; else
                   return k*ln2_hi-((R-(k*ln2_lo+c))-f);
       }
       s = f/(2.0+f); 
       z = s*s;
       R = z*(Lp1+z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7))))));
       if(k==0) return f-(hfsq-s*(hfsq+R)); else
               return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f);
}

Here is the caller graph for this function:


Variable Documentation

double ln2_hi = 6.93147180369123816490e-01 [static]

Definition at line 124 of file s_log1p.c.

double ln2_lo = 1.90821492927058770002e-10 [static]

Definition at line 125 of file s_log1p.c.

double Lp1 = 6.666666666666735130e-01 [static]

Definition at line 127 of file s_log1p.c.

double Lp2 = 3.999999999940941908e-01 [static]

Definition at line 128 of file s_log1p.c.

double Lp3 = 2.857142874366239149e-01 [static]

Definition at line 129 of file s_log1p.c.

double Lp4 = 2.222219843214978396e-01 [static]

Definition at line 130 of file s_log1p.c.

double Lp5 = 1.818357216161805012e-01 [static]

Definition at line 131 of file s_log1p.c.

double Lp6 = 1.531383769920937332e-01 [static]

Definition at line 132 of file s_log1p.c.

double Lp7 = 1.479819860511658591e-01 [static]

Definition at line 133 of file s_log1p.c.

double two54 = 1.80143985094819840000e+16 [static]

Definition at line 126 of file s_log1p.c.

double zero = 0.0 [static]

Definition at line 135 of file s_log1p.c.