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/*=====================================================================*
* Copyright (C) 2011 Paul Mineiro *
* All rights reserved. *
* *
* Redistribution and use in source and binary forms, with *
* or without modification, are permitted provided that the *
* following conditions are met: *
* *
* * Redistributions of source code must retain the *
* above copyright notice, this list of conditions and *
* the following disclaimer. *
* *
* * Redistributions in binary form must reproduce the *
* above copyright notice, this list of conditions and *
* the following disclaimer in the documentation and/or *
* other materials provided with the distribution. *
* *
* * Neither the name of Paul Mineiro nor the names *
* of other contributors may be used to endorse or promote *
* products derived from this software without specific *
* prior written permission. *
* *
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND *
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, *
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES *
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE *
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER *
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, *
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES *
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE *
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR *
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF *
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT *
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY *
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE *
* POSSIBILITY OF SUCH DAMAGE. *
* *
* Contact: Paul Mineiro <paul@mineiro.com> *
*=====================================================================*/
#ifndef __FAST_LOG_H_
#define __FAST_LOG_H_
#include <stdint.h>
#include "sse.h"
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
fastlog (float x)
{
return 0.69314718f * fastlog2 (x);
}
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;
}
static inline float
fasterlog (float x)
{
// return 0.69314718f * fasterlog2 (x);
union { float f; uint32_t i; } vx = { x };
float y = vx.i;
y *= 8.2629582881927490e-8f;
return y - 87.989971088f;
}
#ifdef __SSE2__
static inline v4sf
vfastlog2 (v4sf x)
{
union { v4sf f; v4si i; } vx = { x };
union { v4si i; v4sf f; } mx; mx.i = (vx.i & v4sil (0x007FFFFF)) | v4sil (0x3f000000);
v4sf y = v4si_to_v4sf (vx.i);
y *= v4sfl (1.1920928955078125e-7f);
const v4sf c_124_22551499 = v4sfl (124.22551499f);
const v4sf c_1_498030302 = v4sfl (1.498030302f);
const v4sf c_1_725877999 = v4sfl (1.72587999f);
const v4sf c_0_3520087068 = v4sfl (0.3520887068f);
return y - c_124_22551499
- c_1_498030302 * mx.f
- c_1_725877999 / (c_0_3520087068 + mx.f);
}
static inline v4sf
vfastlog (v4sf x)
{
const v4sf c_0_69314718 = v4sfl (0.69314718f);
return c_0_69314718 * vfastlog2 (x);
}
static inline v4sf
vfasterlog2 (v4sf x)
{
union { v4sf f; v4si i; } vx = { x };
v4sf y = v4si_to_v4sf (vx.i);
y *= v4sfl (1.1920928955078125e-7f);
const v4sf c_126_94269504 = v4sfl (126.94269504f);
return y - c_126_94269504;
}
static inline v4sf
vfasterlog (v4sf x)
{
// const v4sf c_0_69314718 = v4sfl (0.69314718f);
//
// return c_0_69314718 * vfasterlog2 (x);
union { v4sf f; v4si i; } vx = { x };
v4sf y = v4si_to_v4sf (vx.i);
y *= v4sfl (8.2629582881927490e-8f);
const v4sf c_87_989971088 = v4sfl (87.989971088f);
return y - c_87_989971088;
}
#endif // __SSE2__
#endif // __FAST_LOG_H_
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