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// Copyright 2018 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 java.util.Arrays;
/**
* Converts a set of ranges into a graph by counting the number of ranges that are active at any
* point in time. Time is split into equal-sized buckets, and we compute one value per bucket. If a
* range partially overlaps a bucket, then the bucket is incremented by the fraction of overlap.
*/
public class CpuUsageTimeSeries {
private final long startTimeMillis;
private final long bucketSizeMillis;
private static final int INITIAL_SIZE = 100;
private double[] data = new double[INITIAL_SIZE];
public CpuUsageTimeSeries(long startTimeMillis, long bucketSizeMillis) {
this.startTimeMillis = startTimeMillis;
this.bucketSizeMillis = bucketSizeMillis;
}
public void addRange(long startTimeMillis, long endTimeMillis) {
addRange(startTimeMillis, endTimeMillis, /* value= */ 1);
}
/** Adds a new range to the time series, by increasing every affected bucket by value. */
public void addRange(long rangeStartMillis, long rangeEndMillis, double value) {
// Compute times relative to start and their positions in the data array.
rangeStartMillis -= startTimeMillis;
rangeEndMillis -= startTimeMillis;
int startPosition = (int) (rangeStartMillis / bucketSizeMillis);
int endPosition = (int) (rangeEndMillis / bucketSizeMillis);
// Assume we add the following range R:
// ----------------------------------
// | |ssRRR|RRRRR|Reeee| |
// ----------------------------------
// we cannot just add value to each affected bucket but have to correct the values for the first
// and last bucket by calculating the size of 's' and 'e'.
double missingStartFraction =
((double) (rangeStartMillis - bucketSizeMillis * startPosition)) / bucketSizeMillis;
double missingEndFraction =
((double) (bucketSizeMillis * (endPosition + 1) - rangeEndMillis)) / bucketSizeMillis;
if (startPosition < 0) {
startPosition = 0;
missingStartFraction = 0;
}
if (endPosition < startPosition) {
endPosition = startPosition;
missingEndFraction = 0;
}
// Resize data array if necessary so it can at least fit endPosition.
if (endPosition >= data.length) {
data = Arrays.copyOf(data, Math.max(endPosition + 1, 2 * data.length));
}
// Do the actual update.
for (int i = startPosition; i <= endPosition; i++) {
double fraction = 1;
if (i == startPosition) {
fraction -= missingStartFraction;
}
if (i == endPosition) {
fraction -= missingEndFraction;
}
data[i] += fraction * value;
}
}
public double[] toDoubleArray(int len) {
return Arrays.copyOf(data, len);
}
}
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