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      1 /* GENERATED SOURCE. DO NOT MODIFY. */
      2 //  2016 and later: Unicode, Inc. and others.
      3 // License & terms of use: http://www.unicode.org/copyright.html#License
      4 /*
      5  *******************************************************************************
      6  * Copyright (C) 2011-2012, Google, International Business Machines Corporation and
      7  * others. All Rights Reserved.
      8  *******************************************************************************
      9  */
     10 package android.icu.dev.util;
     11 
     12 import android.icu.text.DecimalFormat;
     13 import android.icu.text.NumberFormat;
     14 import android.icu.util.ULocale;
     15 import android.icu.testsharding.MainTestShard;
     16 
     17 @MainTestShard
     18 public final class Timer {
     19     public static final long SECONDS = 100000000;
     20 
     21     private long startTime;
     22     private long duration;
     23     private boolean timing = false;
     24     private int iterations;
     25     private long timingPeriod = 5*SECONDS;
     26     {
     27         start();
     28     }
     29 
     30     public Timer start() {
     31         startTime = System.nanoTime();
     32         timing = true;
     33         duration = Long.MIN_VALUE;
     34         return this;
     35     }
     36 
     37     public long getDuration() {
     38         if (timing) {
     39             duration = System.nanoTime() - startTime;
     40             timing = false;
     41         }
     42         return duration;
     43     }
     44 
     45     public long stop() {
     46         return getDuration();
     47     }
     48 
     49     public int getIterations() {
     50         return iterations;
     51     }
     52 
     53     public long getTimingPeriod() {
     54         return timingPeriod;
     55     }
     56 
     57     public Timer setTimingPeriod(long timingPeriod) {
     58         this.timingPeriod = timingPeriod;
     59         return this;
     60     }
     61 
     62     public DecimalFormat getNumberFormat() {
     63         return nf;
     64     }
     65 
     66     public DecimalFormat getPercentFormat() {
     67         return pf;
     68     }
     69 
     70     public String toString() {
     71         return nf.format(getDuration()) + "\tns";
     72     }
     73     public String toString(Timer other) {
     74         return toString(1L, other.getDuration());
     75     }
     76     public String toString(long iterations) {
     77         return nf.format(getDuration()/iterations) + "\tns";
     78     }
     79 
     80     public String toString(long iterations, long other) {
     81         return nf.format(getDuration()/iterations) + "\tns\t" + pf.format((double)getDuration()/other - 1D) + "";
     82     }
     83 
     84     private DecimalFormat nf = (DecimalFormat) NumberFormat.getNumberInstance(ULocale.ENGLISH);
     85     private DecimalFormat pf = (DecimalFormat) NumberFormat.getPercentInstance(ULocale.ENGLISH);
     86 
     87     {
     88         pf.setMaximumFractionDigits(1);
     89         pf.setPositivePrefix("+");
     90     }
     91 
     92     public abstract static class Loop {
     93         public void init(Object... params) {}
     94         abstract public void time(int repeat);
     95     }
     96 
     97     public long timeIterations(Loop loop, Object... params) {
     98         // Timing on Java is very tricky, especially when you count in garbage collection. This is a simple strategy for now, we might improve later.
     99         // The current strategy is to warm up once, then time it until we reach the timingPeriod (eg 5 seconds), increasing the iterations each time
    100         // At first, we double the iterations.
    101         // Once we get to within 1/4 of the timingPeriod, we change to adding 33%, plus 1. We also remember the shortest duration from this point on.
    102         // We return the shortest of the durations.
    103         loop.init(params);
    104         System.gc();
    105         start();
    106         loop.time(1);
    107         stop();
    108         iterations = 1;
    109         long shortest = Long.MAX_VALUE;
    110         while (true) {
    111             System.gc();
    112             start();
    113             loop.time(iterations);
    114             stop();
    115             if (duration >= timingPeriod) {
    116                 duration /= iterations;
    117                 return Math.min(duration, shortest);
    118             } else if (duration >= timingPeriod / 4) {
    119                 duration /= iterations;
    120                 shortest = Math.min(duration, shortest);
    121                 iterations = (iterations * 4) / 3 + 1;
    122             } else {
    123                 iterations = iterations * 2;
    124             }
    125         }
    126     }
    127 }