39 lines
872 B
C
39 lines
872 B
C
/* Copyright unknown. Code by Laurent de Soras <laurent@ohmforce.com>.
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*/
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#ifndef __pbd_fastlog_h__
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#define __pbd_fastlog_h__
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#include <math.h> /* for HUGE_VAL */
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static inline float fast_log2 (float val)
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{
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/* don't use reinterpret_cast<> because that prevents this
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from being used by pure C code (for example, GnomeCanvasItems)
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*/
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int * const exp_ptr = (int *)(&val);
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int x = *exp_ptr;
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const int log_2 = ((x >> 23) & 255) - 128;
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x &= ~(255 << 23);
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x += 127 << 23;
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*exp_ptr = x;
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val = ((-1.0f/3) * val + 2) * val - 2.0f/3; // (1)
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return (val + log_2);
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}
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static inline float fast_log (const float val)
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{
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return (fast_log2 (val) * 0.69314718f);
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}
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static inline float fast_log10 (const float val)
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{
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return fast_log2(val) / 3.312500f;
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}
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static inline float minus_infinity() { return -HUGE_VAL; }
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#endif /* __pbd_fastlog_h__ */
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