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      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 
     17 package android.perftests.utils;
     18 
     19 import java.util.ArrayList;
     20 import java.util.Collections;
     21 import java.util.List;
     22 
     23 public 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