diff options
author | Robert Jonsson <spamatica@gmail.com> | 2009-12-27 11:30:35 +0000 |
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committer | Robert Jonsson <spamatica@gmail.com> | 2009-12-27 11:30:35 +0000 |
commit | b703eab295330e6f81564fbb39a10a1a2fdd2f54 (patch) | |
tree | e46b5c9a6bc22fd661c15d1d2123f5bf631cef80 /muse_qt4_evolution/awl/fastlog.h | |
parent | 5d5fa0fdf913907edbc3d2d29a7548f0cb658c94 (diff) |
moved old qt4 branch
Diffstat (limited to 'muse_qt4_evolution/awl/fastlog.h')
-rw-r--r-- | muse_qt4_evolution/awl/fastlog.h | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/muse_qt4_evolution/awl/fastlog.h b/muse_qt4_evolution/awl/fastlog.h new file mode 100644 index 00000000..90a85342 --- /dev/null +++ b/muse_qt4_evolution/awl/fastlog.h @@ -0,0 +1,39 @@ +/* Copyright unknown. Code by Laurent de Soras <laurent@ohmforce.com>. + */ + +#ifndef __FASTLOG_H__ +#define __FASTLOG_H__ + +#include <math.h> /* for HUGE_VAL */ + +static inline float fast_log2 (float val) + { + /* don't use reinterpret_cast<> because that prevents this + from being used by pure C code (for example, GnomeCanvasItems) + */ + union {float f; int i;} t; + t.f = val; + int* const exp_ptr = &t.i; + int x = *exp_ptr; + const int log_2 = ((x >> 23) & 255) - 128; + x &= ~(255 << 23); + x += 127 << 23; + *exp_ptr = x; + val = ((-1.0f/3) * t.f + 2) * t.f - 2.0f/3; + return (val + log_2); + } + +static inline float fast_log (const float val) + { + return (fast_log2 (val) * 0.69314718f); + } + +static inline float fast_log10 (const float val) + { + return fast_log2(val) / 3.312500f; + } + +static inline float minus_infinity() { return -HUGE_VAL; } + +#endif + |