| /* |

| * copyright (c) 2016 Ganesh Ajjanagadde <gajjanag@gmail.com> |

| * |

| * This file is part of FFmpeg. |

| * |

| * FFmpeg is free software; you can redistribute it and/or |

| * modify it under the terms of the GNU Lesser General Public |

| * License as published by the Free Software Foundation; either |

| * version 2.1 of the License, or (at your option) any later version. |

| * |

| * FFmpeg 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 |

| * Lesser General Public License for more details. |

| * |

| * You should have received a copy of the GNU Lesser General Public |

| * License along with FFmpeg; if not, write to the Free Software |

| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |

| */ |

| |

| /** |

| * @file |

| * internal math functions header |

| */ |

| |

| #ifndef AVUTIL_FFMATH_H |

| #define AVUTIL_FFMATH_H |

| |

| #include "attributes.h" |

| #include "libm.h" |

| |

| /** |

| * Compute 10^x for floating point values. Note: this function is by no means |

| * "correctly rounded", and is meant as a fast, reasonably accurate approximation. |

| * For instance, maximum relative error for the double precision variant is |

| * ~ 1e-13 for very small and very large values. |

| * This is ~2x faster than GNU libm's approach, which is still off by 2ulp on |

| * some inputs. |

| * @param x exponent |

| * @return 10^x |

| */ |

| static av_always_inline double ff_exp10(double x) |

| { |

| return exp2(M_LOG2_10 * x); |

| } |

| |

| static av_always_inline float ff_exp10f(float x) |

| { |

| return exp2f(M_LOG2_10 * x); |

| } |

| |

| /** |

| * Compute x^y for floating point x, y. Note: this function is faster than the |

| * libm variant due to mainly 2 reasons: |

| * 1. It does not handle any edge cases. In particular, this is only guaranteed |

| * to work correctly for x > 0. |

| * 2. It is not as accurate as a standard nearly "correctly rounded" libm variant. |

| * @param x base |

| * @param y exponent |

| * @return x^y |

| */ |

| static av_always_inline float ff_fast_powf(float x, float y) |

| { |

| return expf(logf(x) * y); |

| } |

| |

| #endif /* AVUTIL_FFMATH_H */ |