diff options
Diffstat (limited to 'Build/source/utils/pmx/pmx-2.6.18/libf2c/z_log.c')
-rw-r--r-- | Build/source/utils/pmx/pmx-2.6.18/libf2c/z_log.c | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/Build/source/utils/pmx/pmx-2.6.18/libf2c/z_log.c b/Build/source/utils/pmx/pmx-2.6.18/libf2c/z_log.c new file mode 100644 index 00000000000..4f11bbe0c78 --- /dev/null +++ b/Build/source/utils/pmx/pmx-2.6.18/libf2c/z_log.c @@ -0,0 +1,121 @@ +#include "f2c.h" + +#ifdef KR_headers +double log(), f__cabs(), atan2(); +#define ANSI(x) () +#else +#define ANSI(x) x +#undef abs +#include "math.h" +#ifdef __cplusplus +extern "C" { +#endif +extern double f__cabs(double, double); +#endif + +#ifndef NO_DOUBLE_EXTENDED +#ifndef GCC_COMPARE_BUG_FIXED +#ifndef Pre20000310 +#ifdef Comment +Some versions of gcc, such as 2.95.3 and 3.0.4, are buggy under -O2 or -O3: +on IA32 (Intel 80x87) systems, they may do comparisons on values computed +in extended-precision registers. This can lead to the test "s > s0" that +was used below being carried out incorrectly. The fix below cannot be +spoiled by overzealous optimization, since the compiler cannot know +whether gcc_bug_bypass_diff_F2C will be nonzero. (We expect it always +to be zero. The weird name is unlikely to collide with anything.) + +An example (provided by Ulrich Jakobus) where the bug fix matters is + + double complex a, b + a = (.1099557428756427618354862829619, .9857360542953131909982289471372) + b = log(a) + +An alternative to the fix below would be to use 53-bit rounding precision, +but the means of specifying this 80x87 feature are highly unportable. +#endif /*Comment*/ +#define BYPASS_GCC_COMPARE_BUG +double (*gcc_bug_bypass_diff_F2C) ANSI((double*,double*)); + static double +#ifdef KR_headers +diff1(a,b) double *a, *b; +#else +diff1(double *a, double *b) +#endif +{ return *a - *b; } +#endif /*Pre20000310*/ +#endif /*GCC_COMPARE_BUG_FIXED*/ +#endif /*NO_DOUBLE_EXTENDED*/ + +#ifdef KR_headers +VOID z_log(r, z) doublecomplex *r, *z; +#else +void z_log(doublecomplex *r, doublecomplex *z) +#endif +{ + double s, s0, t, t2, u, v; + double zi = z->i, zr = z->r; +#ifdef BYPASS_GCC_COMPARE_BUG + double (*diff) ANSI((double*,double*)); +#endif + + r->i = atan2(zi, zr); +#ifdef Pre20000310 + r->r = log( f__cabs( zr, zi ) ); +#else + if (zi < 0) + zi = -zi; + if (zr < 0) + zr = -zr; + if (zr < zi) { + t = zi; + zi = zr; + zr = t; + } + t = zi/zr; + s = zr * sqrt(1 + t*t); + /* now s = f__cabs(zi,zr), and zr = |zr| >= |zi| = zi */ + if ((t = s - 1) < 0) + t = -t; + if (t > .01) + r->r = log(s); + else { + +#ifdef Comment + + log(1+x) = x - x^2/2 + x^3/3 - x^4/4 + - ... + + = x(1 - x/2 + x^2/3 -+...) + + [sqrt(y^2 + z^2) - 1] * [sqrt(y^2 + z^2) + 1] = y^2 + z^2 - 1, so + + sqrt(y^2 + z^2) - 1 = (y^2 + z^2 - 1) / [sqrt(y^2 + z^2) + 1] + +#endif /*Comment*/ + +#ifdef BYPASS_GCC_COMPARE_BUG + if (!(diff = gcc_bug_bypass_diff_F2C)) + diff = diff1; +#endif + t = ((zr*zr - 1.) + zi*zi) / (s + 1); + t2 = t*t; + s = 1. - 0.5*t; + u = v = 1; + do { + s0 = s; + u *= t2; + v += 2; + s += u/v - t*u/(v+1); + } +#ifdef BYPASS_GCC_COMPARE_BUG + while(s - s0 > 1e-18 || (*diff)(&s,&s0) > 0.); +#else + while(s > s0); +#endif + r->r = s*t; + } +#endif + } +#ifdef __cplusplus +} +#endif |