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glibc  2.9
Functions | Variables
e_logf.c File Reference
#include "math.h"
#include "math_private.h"

Go to the source code of this file.

Functions

float __ieee754_logf (float x)

Variables

static float ln2_hi = 6.9313812256e-01
static float ln2_lo = 9.0580006145e-06
static float two25 = 3.355443200e+07
static float Lg1 = 6.6666668653e-01
static float Lg2 = 4.0000000596e-01
static float Lg3 = 2.8571429849e-01
static float Lg4 = 2.2222198546e-01
static float Lg5 = 1.8183572590e-01
static float Lg6 = 1.5313838422e-01
static float Lg7 = 1.4798198640e-01
static float zero = 0.0

Function Documentation

float __ieee754_logf ( float  x)

Definition at line 48 of file e_logf.c.

{
       float hfsq,f,s,z,R,w,t1,t2,dk;
       int32_t k,ix,i,j;

       GET_FLOAT_WORD(ix,x);

       k=0;
       if (ix < 0x00800000) {                    /* x < 2**-126  */
           if ((ix&0x7fffffff)==0)
              return -two25/(x-x);        /* log(+-0)=-inf */
           if (ix<0) return (x-x)/(x-x);  /* log(-#) = NaN */
           k -= 25; x *= two25; /* subnormal number, scale up x */
           GET_FLOAT_WORD(ix,x);
       }
       if (ix >= 0x7f800000) return x+x;
       k += (ix>>23)-127;
       ix &= 0x007fffff;
       i = (ix+(0x95f64<<3))&0x800000;
       SET_FLOAT_WORD(x,ix|(i^0x3f800000));      /* normalize x or x/2 */
       k += (i>>23);
       f = x-(float)1.0;
       if((0x007fffff&(15+ix))<16) {      /* |f| < 2**-20 */
           if(f==zero) {
             if(k==0) return zero;  else {dk=(float)k;
                                      return dk*ln2_hi+dk*ln2_lo;}
           }
           R = f*f*((float)0.5-(float)0.33333333333333333*f);
           if(k==0) return f-R; else {dk=(float)k;
                   return dk*ln2_hi-((R-dk*ln2_lo)-f);}
       }
       s = f/((float)2.0+f);
       dk = (float)k;
       z = s*s;
       i = ix-(0x6147a<<3);
       w = z*z;
       j = (0x6b851<<3)-ix;
       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=(float)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

float Lg1 = 6.6666668653e-01 [static]

Definition at line 31 of file e_logf.c.

float Lg2 = 4.0000000596e-01 [static]

Definition at line 32 of file e_logf.c.

float Lg3 = 2.8571429849e-01 [static]

Definition at line 33 of file e_logf.c.

float Lg4 = 2.2222198546e-01 [static]

Definition at line 34 of file e_logf.c.

float Lg5 = 1.8183572590e-01 [static]

Definition at line 35 of file e_logf.c.

float Lg6 = 1.5313838422e-01 [static]

Definition at line 36 of file e_logf.c.

float Lg7 = 1.4798198640e-01 [static]

Definition at line 37 of file e_logf.c.

float ln2_hi = 6.9313812256e-01 [static]

Definition at line 28 of file e_logf.c.

float ln2_lo = 9.0580006145e-06 [static]

Definition at line 29 of file e_logf.c.

float two25 = 3.355443200e+07 [static]

Definition at line 30 of file e_logf.c.

float zero = 0.0 [static]

Definition at line 42 of file e_logf.c.