/*=====================================================================*
 *                   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 <cstdint>
#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_
