com.google.devtools.build.lib.profiler.SingleStatRecorder.java Source code

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Here is the source code for com.google.devtools.build.lib.profiler.SingleStatRecorder.java

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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.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;
import com.google.devtools.build.lib.util.Preconditions;

/**
 * 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();
    }
}