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implimentation of log2 was taken from here
http://www.freebsd.org/cgi/cvsweb.cgi/ports/graphics/inkscape/files/patch-src_trace_potrace_inkscape-potrace.cpp
http://www.freebsd.org/cgi/query-pr.cgi?pr=83845
--- liboctave/CmplxDET.cc.orig Thu Mar 2 12:40:01 2006
+++ liboctave/CmplxDET.cc Tue Jul 4 21:10:43 2006
@@ -33,6 +33,8 @@
#include "lo-mappers.h"
#include "oct-cmplx.h"
+#include "log2.h"
+
bool
ComplexDET::value_will_overflow (void) const
{
--- liboctave/dbleDET.cc.orig Thu Jul 27 02:19:10 2006
+++ liboctave/dbleDET.cc Thu Aug 31 16:05:44 2006
@@ -29,6 +29,7 @@
#include <cmath>
#include "dbleDET.h"
+#include "log2.h"
#include "lo-mappers.h"
bool
@@ -64,7 +65,7 @@
{
if (c10 != 0.0)
{
- double etmp = e10 / log10 (2);
+ double etmp = e10 / __builtin_log10 (2);
e2 = static_cast<int> (xround (etmp));
etmp -= e2;
c2 = c10 * xexp2 (etmp);
--- /dev/null Tue Jul 4 21:11:00 2006
+++ liboctave/log2.h Tue Jul 4 21:09:55 2006
@@ -0,0 +1,118 @@
+#ifndef log2
+static const double
+ln2 = 0.6931471805599452862268,
+two54 = 1.80143985094819840000e+16, /* 43500000 00000000 */
+Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */
+Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */
+Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */
+Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */
+Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */
+Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */
+Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
+
+static const double zero = 0.0;
+
+#if BYTE_ORDER == BIG_ENDIAN
+
+typedef union
+{
+ double value;
+ struct
+ {
+ u_int32_t msw;
+ u_int32_t lsw;
+ } parts;
+} ieee_double_shape_type;
+
+#endif
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+
+typedef union
+{
+ double value;
+ struct
+ {
+ u_int32_t lsw;
+ u_int32_t msw;
+ } parts;
+} ieee_double_shape_type;
+
+#endif
+
+#define EXTRACT_WORDS(ix0,ix1,d) \
+ do { \
+ ieee_double_shape_type ew_u; \
+ ew_u.value = (d); \
+ (ix0) = ew_u.parts.msw; \
+ (ix1) = ew_u.parts.lsw; \
+ } while (0)
+
+#define GET_HIGH_WORD(i,d) \
+ do { \
+ ieee_double_shape_type gh_u; \
+ gh_u.value = (d); \
+ (i) = gh_u.parts.msw; \
+ } while (0)
+
+#define SET_HIGH_WORD(d,v) \
+ do { \
+ ieee_double_shape_type sh_u; \
+ sh_u.value = (d); \
+ sh_u.parts.msw = (v); \
+ (d) = sh_u.value; \
+ } while (0)
+
+static double
+_log2(double x)
+{
+ double hfsq,f,s,z,R,w,t1,t2,dk;
+ int32_t k,hx,i,j;
+ u_int32_t lx;
+
+ EXTRACT_WORDS(hx,lx,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 */
+ GET_HIGH_WORD(hx,x);
+ }
+ if (hx >= 0x7ff00000) return x+x;
+ k += (hx>>20)-1023;
+ hx &= 0x000fffff;
+ i = (hx+0x95f64)&0x100000;
+ SET_HIGH_WORD(x,hx|(i^0x3ff00000)); /* normalize x or x/2 */
+ k += (i>>20);
+ f = x-1.0;
+ dk = (double)k;
+ if((0x000fffff&(2+hx))<3) { /* |f| < 2**-20 */
+ if (f==zero)
+ return (dk);
+ R = f*f*(0.5-0.33333333333333333*f);
+ return (dk-(R-f)/ln2);
+ }
+ s = f/(2.0+f);
+ 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;
+ return (dk-(hfsq-s*(hfsq+R)-f)/ln2);
+ } else
+ return (dk-((s*(f-R))-f)/ln2);
+}
+
+#define log2(x) _log2(x)
+#endif
+
+
+
+
k
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