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
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
/*
* Copyright 2023 The original authors
*
* 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 dev.morling.onebrc;
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.util.stream.*;
import java.util.*;
/* A simple implementation that memory maps the file, reads chunks in parallel and minimises allocation without any unsafe.
*
* Timings on 4 core i7-7500U CPU @ 2.70GHz:
* average_baseline: 4m48s
* ianopolous: 48s
*/
public class CalculateAverage_ianopolous {
public static final int MAX_LINE_LENGTH = 107;
public static final int MAX_STATIONS = 10000;
public static void main(String[] args) {
File input = new File("./measurements.txt");
long filesize = input.length();
long chunkSize = 256 * 1024 * 1024;
int nChunks = (int) ((filesize + chunkSize - 1) / chunkSize);
List<HashMap<String, Stat>> allResults = IntStream.range(0, nChunks).mapToObj(i -> {
HashMap<String, Stat> results = new HashMap(512);
parseStats(i * chunkSize, Math.min((i + 1) * chunkSize, filesize), results);
return results;
}).parallel().toList();
HashMap<String, Stat> result = allResults.getFirst();
for (int i = 1; i < allResults.size(); ++i) {
for (Map.Entry<String, Stat> entry : allResults.get(i).entrySet()) {
Stat current = result.putIfAbsent(entry.getKey(), entry.getValue());
if (current != null) {
current.merge(entry.getValue());
}
}
}
System.out.println(new TreeMap<>(result));
}
public record Station(String name, ByteBuffer buf) {
}
public static boolean matchingStationBytes(int start, int end, MappedByteBuffer buffer, Station existing) {
buffer.position(start);
for (int i = start; i < end; i++) {
if (existing.buf.get(i - start) != buffer.get(i))
return false;
}
return true;
}
public static Station parseStation(int start, int end, int hash, MappedByteBuffer buffer, List<List<Station>> stations) {
int index = Math.floorMod(hash, MAX_STATIONS);
List<Station> matches = stations.get(index);
if (matches == null) {
List<Station> value = new ArrayList<>();
byte[] stationBuffer = new byte[end - start];
buffer.position(start);
buffer.get(stationBuffer);
String name = new String(stationBuffer);
Station res = new Station(name, ByteBuffer.wrap(stationBuffer));
value.add(res);
stations.set(index, value);
return res;
}
else {
for (int i = 0; i < matches.size(); i++) {
Station s = matches.get(i);
if (matchingStationBytes(start, end, buffer, s))
return s;
}
byte[] stationBuffer = new byte[end - start];
buffer.position(start);
buffer.get(stationBuffer);
Station res = new Station(new String(stationBuffer), ByteBuffer.wrap(stationBuffer));
matches.add(res);
return res;
}
}
public static void parseStats(long startByte, long endByte, Map<String, Stat> results) {
try {
RandomAccessFile file = new RandomAccessFile("./measurements.txt", "r");
long maxEnd = Math.min(file.length(), endByte + MAX_LINE_LENGTH);
long len = maxEnd - startByte;
if (len > Integer.MAX_VALUE)
throw new RuntimeException("Segment size must fit into an int");
int maxDone = (int) (endByte - startByte);
MappedByteBuffer buffer = file.getChannel().map(FileChannel.MapMode.READ_ONLY, startByte, len);
int done = 0;
// read first partial line
if (startByte > 0) {
for (int i = 0; i < MAX_LINE_LENGTH; i++) {
byte b = buffer.get(i);
if (b == '\n') {
done = i + 1;
break;
}
}
}
List<List<Station>> stations = new ArrayList<>(MAX_STATIONS);
for (int i = 0; i < MAX_STATIONS; i++)
stations.add(null);
int lineStart = done;
int lineSplit = 0;
long temperature = 0;
int hash = 1;
boolean negative = false;
while (done < maxDone) {
Station station = null;
for (int i = done; i < done + MAX_LINE_LENGTH && i < maxEnd; i++) {
byte b = buffer.get(i);
if (b == '\n') {
done = i + 1;
Stat res = results.get(station.name);
temperature = negative ? -temperature : temperature;
if (res != null) {
res.add(temperature);
}
else {
res = new Stat();
res.add(temperature);
results.put(station.name, res);
}
lineStart = done;
station = null;
hash = 1;
break;
}
else if (b == ';') {
lineSplit = i;
station = parseStation(lineStart, lineSplit, hash, buffer, stations);
temperature = 0;
negative = false;
}
else if (b == '-' && station != null) {
negative = true;
}
else if (b != '.' && station != null) {
temperature = temperature * 10 + (b - 0x30);
}
else {
hash = 31 * hash + b;
}
}
}
}
catch (IOException e) {
throw new RuntimeException(e);
}
}
public static class Stat {
long min = Long.MAX_VALUE, max = Long.MIN_VALUE, total = 0, count = 0;
public void add(long value) {
if (value < min)
min = value;
if (value > max)
max = value;
total += value;
count++;
}
public void merge(Stat value) {
if (value.min < min)
min = value.min;
if (value.max > max)
max = value.max;
total += value.total;
count += value.count;
}
private static double round(double value) {
return Math.round(value) / 10.0;
}
public String toString() {
return round((double) min) + "/" + round(((double) total) / count) + "/" + round((double) max);
}
}
}
|
