1/*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.perftests.utils;
18
19import java.util.ArrayList;
20import java.util.Collections;
21import java.util.List;
22
23public class Stats {
24    private long mMedian, mMin, mMax, mPercentile90, mPercentile95;
25    private double mMean, mStandardDeviation;
26
27    /* Calculate stats in constructor. */
28    public Stats(List<Long> values) {
29        // make a copy since we're modifying it
30        values = new ArrayList<>(values);
31        final int size = values.size();
32        if (size < 2) {
33            throw new IllegalArgumentException("At least two results are necessary.");
34        }
35
36        Collections.sort(values);
37
38        mMin = values.get(0);
39        mMax = values.get(values.size() - 1);
40
41        mMedian = size % 2 == 0 ? (values.get(size / 2) + values.get(size / 2 - 1)) / 2 :
42                values.get(size / 2);
43        mPercentile90 = getPercentile(values, 90);
44        mPercentile95 = getPercentile(values, 95);
45
46        for (int i = 0; i < size; ++i) {
47            long result = values.get(i);
48            mMean += result;
49        }
50        mMean /= (double) size;
51
52        for (int i = 0; i < size; ++i) {
53            final double tmp = values.get(i) - mMean;
54            mStandardDeviation += tmp * tmp;
55        }
56        mStandardDeviation = Math.sqrt(mStandardDeviation / (double) (size - 1));
57    }
58
59    public double getMean() {
60        return mMean;
61    }
62
63    public long getMedian() {
64        return mMedian;
65    }
66
67    public long getMax() {
68        return mMax;
69    }
70
71    public long getMin() {
72        return mMin;
73    }
74
75    public double getStandardDeviation() {
76        return mStandardDeviation;
77    }
78
79    public long getPercentile90() {
80        return mPercentile90;
81    }
82
83    public long getPercentile95() {
84        return mPercentile95;
85    }
86
87    private static long getPercentile(List<Long> values, int percentile) {
88        if (percentile < 0 || percentile > 100) {
89            throw new IllegalArgumentException(
90                    "invalid percentile " + percentile + ", should be 0-100");
91        }
92        int idx = (values.size() - 1) * percentile / 100;
93        return values.get(idx);
94    }
95}
96