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/* Copyright unknown. Code by Laurent de Soras <laurent@ohmforce.com>.
* This file is licensed under the WTFPL v2 license.
* http://www.wtfpl.net/about/
*/
#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
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