1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef LE_FX_ENGINE_COMMON_CORE_MATH_H_
18#define LE_FX_ENGINE_COMMON_CORE_MATH_H_
19
20#include <math.h>
21#include <algorithm>
22using ::std::min;
23using ::std::max;
24using ::std::fill;
25using ::std::fill_n;using ::std::lower_bound;
26#include <cmath>
27#include <math.h>
28//using ::std::fpclassify;
29
30#include "common/core/os.h"
31#include "common/core/types.h"
32
33namespace le_fx {
34namespace math {
35
36// A fast approximation to log2(.)
37inline float fast_log2(float val) {
38  int* const exp_ptr = reinterpret_cast <int *> (&val);
39  int x = *exp_ptr;
40  const int log_2 = ((x >> 23) & 255) - 128;
41  x &= ~(255 << 23);
42  x += 127 << 23;
43  *exp_ptr = x;
44  val = ((-1.0f / 3) * val + 2) * val - 2.0f / 3;
45  return static_cast<float>(val + log_2);
46}
47
48// A fast approximation to log(.)
49inline float fast_log(float val) {
50  return fast_log2(val) *
51      0.693147180559945286226763982995180413126945495605468750f;
52}
53
54// An approximation of the exp(.) function using a 5-th order Taylor expansion.
55// It's pretty accurate between +-0.1 and accurate to 10e-3 between +-1
56template <typename T>
57inline T ExpApproximationViaTaylorExpansionOrder5(T x) {
58  const T x2 = x * x;
59  const T x3 = x2 * x;
60  const T x4 = x2 * x2;
61  const T x5 = x3 * x2;
62  return 1.0f + x + 0.5f * x2 +
63      0.16666666666666665741480812812369549646973609924316406250f * x3 +
64      0.0416666666666666643537020320309238741174340248107910156250f * x4 +
65      0.008333333333333333217685101601546193705871701240539550781250f * x5;
66}
67
68}  // namespace math
69}  // namespace le_fx
70
71// Math functions missing in Android NDK:
72#if defined(LE_FX_OS_ANDROID)
73
74namespace std {
75
76//
77// Round to the nearest integer: We need this implementation
78// since std::round is missing on android.
79//
80template <typename T>
81inline T round(const T &x) {
82  return static_cast<T>(std::floor(static_cast<double>(x) + 0.5));
83}
84
85}  // namespace std
86
87#endif  // LE_FX_OS_ANDROID
88
89#endif  // LE_FX_ENGINE_COMMON_CORE_MATH_H_
90