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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.statistics;
/**
* A running set of samples for a Value instance. It is
* used only in a very specific context between the sampling threads (each instance
* is only used by on sampling thread) and the single logging thread.
*
* @author <a href="mailto:steinar@yahoo-inc.com">Steinar Knutsen</a>
*/
final class SampleSet {
Sampling values;
final Limits histogramLimits;
private boolean isRegisteredForLogging = false;
SampleSet(Limits histogramLimits) {
this.histogramLimits = histogramLimits;
values = new Sampling(0.0d, 0L, 0.0d, 0.0d, histogramLimits);
}
static final class Sampling {
final double sum;
final long insertions;
final double max;
final double min;
final Histogram histogram;
Sampling(double sum, long insertions, double max, double min, Limits histogramLimits) {
if (histogramLimits != null) {
this.histogram = new Histogram(histogramLimits);
} else {
this.histogram = null;
}
this.sum = sum;
this.insertions = insertions;
this.max = max;
this.min = min;
}
Sampling(double sum, long insertions, double max, double min, Histogram histogram) {
this.histogram = histogram;
this.sum = sum;
this.insertions = insertions;
this.max = max;
this.min = min;
}
}
private Sampling createSampling(double x, Sampling previous) {
double sum = previous.sum;
long insertions = previous.insertions;
double max = previous.max;
double min = previous.min;
sum += x;
if (insertions == 0) {
max = x;
min = x;
} else {
max = Math.max(x, max);
min = Math.min(x, min);
}
insertions++;
return new Sampling(sum, insertions, max, min, previous.histogram);
}
/**
* Insert x, do all pertinent operations. (Update histogram, update
* insertion count for calculating mean, etc.)
*
* @return whether this is registered for logging
*/
synchronized boolean put(double x) {
Sampling previous = values;
Histogram histogram = previous.histogram;
if (histogram != null) {
histogram.put(new double[] {x});
}
values = createSampling(x, previous);
return isRegisteredForLogging;
}
/**
* Get state and reset it.
*/
synchronized Sampling getAndReset() {
Sampling previous = values;
values = new Sampling(0.0d, 0L, 0.0d, 0.0d, histogramLimits);
setRegisteredForLogging(false);
return previous;
}
// Setting this state is protected by SampleDirectory.directoryLock. It is
// either set from the logging thread (protected by directoryLock and using
// "this" as a memory barrier through getAndReset()), or from the sampling
// thread protected by directoryLock and without a mem barrier.
void setRegisteredForLogging(boolean isRegisteredForLogging) {
this.isRegisteredForLogging = isRegisteredForLogging;
}
}
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