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/*
* Copyright 2009 Phil Burk, Mobileer Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.jsyn.unitgen;
import com.jsyn.ports.UnitInputPort;
import com.jsyn.ports.UnitVariablePort;
/**
* Output approaches Input exponentially. This unit provides a slowly changing value that approaches
* its Input value exponentially. The equation is:
*
* <PRE>
* Output = Output + Rate * (Input - Output);
* </PRE>
*
* Note that the output may never reach the value of the input. It approaches the input
* asymptotically. The Rate is calculated internally based on the value on the halfLife port. Rate
* is generally just slightly less than 1.0.
*
* @author Phil Burk (C) 2009 Mobileer Inc
* @version 016
* @see LinearRamp
* @see ExponentialRamp
* @see ContinuousRamp
*/
public class AsymptoticRamp extends UnitFilter {
public UnitVariablePort current;
public UnitInputPort halfLife;
private double previousHalfLife = -1.0;
private double decayScalar = 0.99;
/* Define Unit Ports used by connect() and set(). */
public AsymptoticRamp() {
addPort(halfLife = new UnitInputPort(1, "HalfLife", 0.1));
addPort(current = new UnitVariablePort("Current"));
}
@Override
public void generate(int start, int limit) {
double[] outputs = output.getValues();
double[] inputs = input.getValues();
double currentHalfLife = halfLife.getValues()[0];
double currentValue = current.getValue();
double inputValue = currentValue;
if (currentHalfLife != previousHalfLife) {
decayScalar = this.convertHalfLifeToMultiplier(currentHalfLife);
previousHalfLife = currentHalfLife;
}
for (int i = start; i < limit; i++) {
inputValue = inputs[i];
currentValue = currentValue + decayScalar * (inputValue - currentValue);
outputs[i] = currentValue;
}
/*
* When current gets close to input, set current to input to prevent FP underflow, which can
* cause a severe performance degradation in 'C'.
*/
if (Math.abs(inputValue - currentValue) < VERY_SMALL_FLOAT) {
currentValue = inputValue;
}
current.setValue(currentValue);
}
}
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