/*=====================================================================*
 *                   Copyright (C) 2011 Paul Mineiro                   *
 * All rights reserved.                                                *
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 * Redistribution and use in source and binary forms, with             *
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 *     above copyright notice, this list of conditions and             *
 *     the following disclaimer.                                       *
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 *     * Redistributions in binary form must reproduce the             *
 *     above copyright notice, this list of conditions and             *
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 *     other materials provided with the distribution.                 *
 *                                                                     *
 *     * Neither the name of Paul Mineiro nor the names                *
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 *     products derived from this software without specific            *
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 * 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             *
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 * Contact: Paul Mineiro <paul@mineiro.com>                            *
 *=====================================================================*/

#ifndef __FAST_EXP_H_
#define __FAST_EXP_H_

#include <stdint.h>

// Underflow of exponential is common practice in numerical routines,
// so handle it here.

static inline float
fastpow2 (float p)
{
  float offset = (p < 0) ? 1.0f : 0.0f;
  float clipp = (p < -126) ? -126.0f : p;
  int w = clipp;
  float z = clipp - w + offset;
  union { uint32_t i; float f; } v = { static_cast<uint32_t> ( (1 << 23) * (clipp + 121.2740575f + 27.7280233f / (4.84252568f - z) - 1.49012907f * z) ) };

  return v.f;
}

static inline float
fastexp (float p)
{
  return fastpow2 (1.442695040f * p);
}

#endif // __FAST_EXP_H_
