fastlog.h

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/*=====================================================================*
 *                   Copyright (C) 2011 Paul Mineiro                   *
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#ifndef __FAST_LOG_H_
#define __FAST_LOG_H_
 
#include <stdint.h>
 
namespace YODA {
  namespace Utils {
    static inline float 
      fastlog2 (float x)
      {
        union { float f; uint32_t i; } vx = { x };
        union { uint32_t i; float f; } mx = { (vx.i & 0x007FFFFF) | 0x3f000000 };
        float y = vx.i;
        y *= 1.1920928955078125e-7f;
 
        return y - 124.22551499f
          - 1.498030302f * mx.f 
          - 1.72587999f / (0.3520887068f + mx.f);
      }
 
    static inline float 
      fasterlog2 (float x)
      {
        union { float f; uint32_t i; } vx = { x };
        float y = vx.i;
        y *= 1.1920928955078125e-7f;
        return y - 126.94269504f;
      }
  }
}
#endif // __FAST_LOG_H_