nars.util.meter.event.PeriodMeter.java Source code

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Here is the source code for nars.util.meter.event.PeriodMeter.java

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package nars.util.meter.event;

import nars.util.meter.FunctionMeter;
import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;

/**
 * Measures the period between hit() calls to determine frequency-related
 * statistics of hit intervals.
 * millisecond resolution performs better than nanoseconds but both are
 * converted to a double value (nanosecond unixtime) for calculation.
 * 
 * the results can be returned either as period duration (sec) or frequency (1/period).
 */
public class PeriodMeter extends FunctionMeter<Double> {

    double lastReset;
    private final boolean nanoSeconds;
    final DescriptiveStatistics stat;
    private final double window;
    private double prev;
    private final boolean frequency;

    public PeriodMeter(String id, boolean nanoSeconds, double windowSec, boolean asFrequency) {
        super(id, true, ".min", ".max", ".mean", ".stddev");

        window = windowSec * 1.0E9;
        stat = new DescriptiveStatistics();
        this.nanoSeconds = nanoSeconds;
        frequency = asFrequency;
        reset();
    }

    public static double now(boolean nanoSeconds /* TODO use a Resolution enum */) {
        return nanoSeconds ? System.nanoTime() : System.currentTimeMillis() * 1.0E6;
    }

    public double sinceStart() {
        return now(nanoSeconds) - lastReset;
    }

    public double reset() {
        lastReset = now(nanoSeconds);
        stat.clear();
        return lastReset;
    }

    public DescriptiveStatistics hit() {
        double now;
        now = sinceStart() > window ? reset() : now(nanoSeconds);
        if (Double.isFinite(prev)) {
            double dt = now - prev;
            stat.addValue(dt);
        }
        prev = now;
        return stat;
    }

    @Override
    public Double getValue(Object key, int index) {
        if (stat.getN() == 0)
            return null;
        switch (index) {
        case 0:
            return f(stat.getMin());
        case 1:
            return f(stat.getMax());
        case 2:
            return f(stat.getMean());
        case 4:
            return stat.getStandardDeviation();
        }
        return null;
    }

    protected double f(double period) {
        if (frequency) {
            if (period == 0)
                return Double.POSITIVE_INFINITY;
            return 1.0 / period;
        }
        return period;
    }

}