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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.lib.profiler;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Range;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.profiler.MetricData.HistogramElement;
/**
* A stat recorder that can record time histograms, count of calls, average time, Std. Deviation
* and max time.
*/
@ThreadSafe
public class SingleStatRecorder implements StatRecorder {
private final int buckets;
private final Object description;
private int[] histogram;
private int count = 0;
private double avg = 0.0;
private double m2 = 0.0;
private int max = -1;
public SingleStatRecorder(Object description, int buckets) {
this.description = description;
Preconditions.checkArgument(buckets > 1, "At least two buckets (one for bellow start and one"
+ "for above start) are required");
this.buckets = buckets;
histogram = new int[buckets];
}
/** Create an snapshot of the the stats recorded up to now. */
public MetricData snapshot() {
synchronized (this) {
ImmutableList.Builder<HistogramElement> result = ImmutableList.builder();
result.add(new HistogramElement(Range.closedOpen(0, 1), histogram[0]));
int from = 1;
for (int i = 1; i < histogram.length - 1; i++) {
int to = from << 1;
result.add(new HistogramElement(Range.closedOpen(from, to), histogram[i]));
from = to;
}
result.add(new HistogramElement(Range.atLeast(from), histogram[histogram.length - 1]));
return new MetricData(description, result.build(), count, avg,
Math.sqrt(m2 / (double) count), max);
}
}
@Override
public void addStat(int duration, Object obj) {
int histogramBucket = Math.min(32 - Integer.numberOfLeadingZeros(duration), buckets - 1);
synchronized (this) {
count++;
double delta = duration - avg;
avg += delta / count;
m2 += delta * (duration - avg);
if (duration > max) {
max = duration;
}
histogram[histogramBucket]++;
}
}
@Override
public boolean isEmpty() {
return snapshot().getCount() == 0;
}
@Override
public String toString() {
return snapshot().toString();
}
}
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