BogaudioModules

commit 0ee7d565d5986051c38d2b2a3e439221492eb7cb
parent c2e896a32a36a34fd536f3b1218c35238dad7ef1
Author: Matt Demanett <matt@demanett.net>
Date:   Thu,  4 Jan 2018 22:41:57 -0500

Approximately double speed of sine oscillator in benchmark by rewriting it to allow vectorization.

Diffstat:
M
src/dsp/oscillator.cpp
 | 
27
+++++++++++++++++++++------
M
src/dsp/oscillator.hpp
 | 
16
++++++++++------

2 files changed, 31 insertions(+), 12 deletions(-)
diff --git a/src/dsp/oscillator.cpp b/src/dsp/oscillator.cpp
@@ -8,13 +8,28 @@ void SineOscillator::updateDeltaTheta() {
 	float sampleTime = 1.0 / _sampleRate;
 	float cycleTime = 1.0 / _frequency;
 	float _deltaTheta = (sampleTime / cycleTime) * 2.0f * M_PI;
-	_sinDeltaTheta = sinf(_deltaTheta);
-	_cosDeltaTheta = cosf(_deltaTheta);
+	for (int i = 0; i < _n; ++i) {
+		_sinDeltaTheta[i] = sinf((i + 1) * _deltaTheta);
+		_cosDeltaTheta[i] = cosf((i + 1) * _deltaTheta);
+	}
 }
 
 float SineOscillator::_next() {
-	float x2 = _x*_cosDeltaTheta - _y*_sinDeltaTheta;
-	_y = _x*_sinDeltaTheta + _y*_cosDeltaTheta;
-	_x = x2;
-	return _y;
+	if (_step == 0) {
+		const int n1 = _n - 1;
+		for (int i = 0; i < n1; ++i) {
+			_x[i] = _x[n1];
+			_y[i] = _y[n1];
+		}
+
+		float t[_n];
+		for (int i = 0; i < _n; ++i) {
+			t[i] = _x[i]*_cosDeltaTheta[i] - _y[i]*_sinDeltaTheta[i];
+			_y[i] = _x[i]*_sinDeltaTheta[i] + _y[i]*_cosDeltaTheta[i];
+			_x[i] = t[i];
+		}
+	}
+	float out = _y[_step];
+	_step = ++_step % _n;
+	return out;
 }
diff --git a/src/dsp/oscillator.hpp b/src/dsp/oscillator.hpp
@@ -35,10 +35,12 @@ struct OscillatorGenerator : Generator {
 };
 
 struct SineOscillator : OscillatorGenerator {
-	float _x;
-	float _y;
-	float _sinDeltaTheta;
-	float _cosDeltaTheta;
+	static const int _n = 4;
+	int _step = 0;
+	float _x[_n];
+	float _y[_n];
+	float _sinDeltaTheta[_n];
+	float _cosDeltaTheta[_n];
 
 	SineOscillator(
 		float sampleRate,
@@ -46,9 +48,11 @@ struct SineOscillator : OscillatorGenerator {
 		float amplitude = 1.0
 	)
 	: OscillatorGenerator(sampleRate, frequency)
-	, _x(amplitude)
-	, _y(0.0)
 	{
+		for (int i = 0; i < _n; ++i) {
+			_x[i] = amplitude;
+			_y[i] = 0.0;
+		}
 		updateDeltaTheta();
 	}