1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
/**
* Copyright (C) 2009 Google Inc.
*
* 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.caliper;
import static com.google.common.base.Preconditions.checkArgument;
/**
* Measure's the benchmark's per-trial execution time.
*/
class Caliper {
private final long warmupNanos;
private final long runNanos;
Caliper(long warmupMillis, long runMillis) {
checkArgument(warmupMillis > 50);
checkArgument(runMillis > 50);
this.warmupNanos = warmupMillis * 1000000;
this.runNanos = runMillis * 1000000;
}
public double warmUp(TimedRunnable timedRunnable) throws Exception {
long startNanos = System.nanoTime();
long endNanos = startNanos + warmupNanos;
long currentNanos;
int netReps = 0;
int reps = 1;
/*
* Run progressively more reps at a time until we cross our warmup
* threshold. This way any just-in-time compiler will be comfortable running
* multiple iterations of our measurement method.
*/
while ((currentNanos = System.nanoTime()) < endNanos) {
timedRunnable.run(reps);
netReps += reps;
reps *= 2;
}
double nanosPerExecution = (currentNanos - startNanos) / (double) netReps;
if (nanosPerExecution > 1000000000 || nanosPerExecution < 2) {
throw new ConfigurationException("Runtime " + nanosPerExecution + " out of range");
}
return nanosPerExecution;
}
/**
* In the run proper, we predict how extrapolate based on warmup how many
* runs we're going to need, and run them all in a single batch.
*/
public double run(TimedRunnable test, double estimatedNanosPerTrial)
throws Exception {
@SuppressWarnings("NumericCastThatLosesPrecision")
int trials = (int) (runNanos / estimatedNanosPerTrial);
if (trials == 0) {
trials = 1;
}
double nanosPerTrial = measure(test, trials);
// if the runtime was in the expected range, return it. We're good.
if (isPlausible(estimatedNanosPerTrial, nanosPerTrial)) {
return nanosPerTrial;
}
// The runtime was outside of the expected range. Perhaps the VM is inlining
// things too aggressively? We'll run more rounds to confirm that the
// runtime scales with the number of trials.
double nanosPerTrial2 = measure(test, trials * 4);
if (isPlausible(nanosPerTrial, nanosPerTrial2)) {
return nanosPerTrial;
}
throw new ConfigurationException("Measurement error: "
+ "runtime isn't proportional to the number of repetitions!");
}
/**
* Returns true if the given measurement is consistent with the expected
* measurement.
*/
private boolean isPlausible(double expected, double measurement) {
double ratio = measurement / expected;
return ratio > 0.5 && ratio < 2.0;
}
private double measure(TimedRunnable test, int trials) throws Exception {
prepareForTest();
long startNanos = System.nanoTime();
test.run(trials);
return (System.nanoTime() - startNanos) / (double) trials;
}
private void prepareForTest() {
System.gc();
System.gc();
}
}
|
