1 /*
2  *  Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef MODULES_AUDIO_PROCESSING_NS_FAST_MATH_H_
12 #define MODULES_AUDIO_PROCESSING_NS_FAST_MATH_H_
13 
14 #include "api/array_view.h"
15 
16 namespace webrtc {
17 
18 // Sqrt approximation.
19 float SqrtFastApproximation(float f);
20 
21 // Log base conversion log(x) = log2(x)/log2(e).
22 float LogApproximation(float x);
23 void LogApproximation(rtc::ArrayView<const float> x, rtc::ArrayView<float> y);
24 
25 // 2^x approximation.
26 float Pow2Approximation(float p);
27 
28 // x^p approximation.
29 float PowApproximation(float x, float p);
30 
31 // e^x approximation.
32 float ExpApproximation(float x);
33 void ExpApproximation(rtc::ArrayView<const float> x, rtc::ArrayView<float> y);
34 void ExpApproximationSignFlip(rtc::ArrayView<const float> x,
35                               rtc::ArrayView<float> y);
36 }  // namespace webrtc
37 
38 #endif  // MODULES_AUDIO_PROCESSING_NS_FAST_MATH_H_
39