openmp_maths.h

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/*
   This file is part of darktable,
   Copyright (C) 2020-2021 Aurélien PIERRE.
   Copyright (C) 2021 Ralf Brown.
   Copyright (C) 2022 Martin Bařinka.
   
   darktable is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
   
   darktable is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with darktable.  If not, see <http://www.gnu.org/licenses/>.
*/
 
 
#include <glib.h>            // for inline
#include <math.h>            // for log, logf, powf
 
#pragma once
 
 
#if defined(_OPENMP) && !defined(_WIN32) && !defined(__GNUC__)
 
#pragma omp declare simd
extern float fmaxf(const float x, const float y);
 
#pragma omp declare simd
extern float fminf(const float x, const float y);
 
#pragma omp declare simd
extern float fabsf(const float x);
 
#pragma omp declare simd
extern float powf(const float x, const float y);
 
#pragma omp declare simd
extern float sqrtf(const float x);
 
#pragma omp declare simd
extern float cbrtf(const float x);
 
#pragma omp declare simd
extern float log2f(const float x);
 
#pragma omp declare simd
extern float exp2f(const float x);
 
#pragma omp declare simd
extern float log10f(const float x);
 
#pragma omp declare simd
extern float expf(const float x);
 
#pragma omp declare simd
extern float logf(const float x);
 
#endif
 
 
/* Bring our own optimized maths functions because Clang makes dumb shit */
 
__OMP_DECLARE_SIMD__()
static inline float fast_exp10f(const float x)
{
  // we use the property : 10^x = exp(log(10) * x) = 2^(log(10) * x / log(2))
  // max relative error over x = [0; 4] is 1.5617955706227326e-15
  return exp2f(3.3219280948873626f * x);
}
 
// Since we are at it, write an optimized expf
__OMP_DECLARE_SIMD__()
static inline float fast_expf(const float x)
{
  // we use the property : exp(x) = 2^(x / log(2))
  // max relative error over x = [0; 4] is 5.246203046472202e-16
  return exp2f(1.4426950408889634f * x);
}
 
 
__OMP_DECLARE_SIMD__(aligned(vector:16))
static inline float v_maxf(const float vector[3])
{
  // Find the max over an RGB vector
  return fmaxf(fmaxf(vector[0], vector[1]), vector[2]);
}
 
 
__OMP_DECLARE_SIMD__(aligned(vector:16))
static inline float v_minf(const float vector[3])
{
  // Find the min over an RGB vector
  return fminf(fminf(vector[0], vector[1]), vector[2]);
}
 
__OMP_DECLARE_SIMD__(aligned(vector:16))
static inline float v_sumf(const float vector[3])
{
  return vector[0] + vector[1] + vector[2];
}
 
 
__OMP_DECLARE_SIMD__()
static inline float fmaxabsf(const float a, const float b)
{
  // Find the max in absolute value and return it with its sign
  return (fabsf(a) > fabsf(b) && !isnan(a)) ? a :
                                            (isnan(b)) ? 0.f : b;
}
 
 
__OMP_DECLARE_SIMD__()
static inline float fminabsf(const float a, const float b)
{
  // Find the min in absolute value and return it with its sign
  return (fabsf(a) < fabsf(b) && !isnan(a)) ? a :
                                            (isnan(b)) ? 0.f : b;
}
 
 
__OMP_DECLARE_SIMD__()
static inline float clamp_simd(const float x)
{
  return fminf(fmaxf(x, 0.0f), 1.0f);
}
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