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
202
|
/*
* 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.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteOrder;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.TreeMap;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
public class CalculateAverage_kuduwa_keshavram {
private static final String FILE = "./measurements.txt";
public static void main(String[] args) throws IOException, InterruptedException {
TreeMap<String, Measurement> resultMap = getFileSegments(new File(FILE)).stream()
.parallel()
.map(
segment -> {
final Measurement[][] measurements = new Measurement[1024 * 128][3];
try (FileChannel fileChannel = (FileChannel) Files.newByteChannel(Path.of(FILE), StandardOpenOption.READ)) {
MappedByteBuffer byteBuffer = fileChannel.map(
MapMode.READ_ONLY, segment.start, segment.end - segment.start);
byteBuffer.order(ByteOrder.nativeOrder());
while (byteBuffer.hasRemaining()) {
byte[] city = new byte[100];
byte b;
int hash = 0;
int i = 0;
while ((b = byteBuffer.get()) != 59) {
hash = 31 * hash + b;
city[i++] = b;
}
byte[] newCity = new byte[i];
System.arraycopy(city, 0, newCity, 0, i);
int measurement = 0;
boolean negative = false;
while ((b = byteBuffer.get()) != 10) {
if (b == 45) {
negative = true;
}
else if (b == 46) {
// skip
}
else {
final int n = b - '0';
measurement = measurement * 10 + n;
}
}
putOrMerge(
measurements,
new Measurement(
hash, newCity, negative ? measurement * -1 : measurement));
}
}
catch (IOException e) {
throw new RuntimeException(e);
}
return measurements;
})
.flatMap(measurements -> Arrays.stream(measurements).flatMap(Arrays::stream))
.filter(Objects::nonNull)
.collect(
Collectors.toMap(
measurement -> new String(measurement.city),
Function.identity(),
(m1, m2) -> {
m1.merge(m2);
return m1;
},
TreeMap::new));
System.out.println(resultMap);
}
private static void putOrMerge(Measurement[][] measurements, Measurement measurement) {
int index = measurement.hash & (measurements.length - 1);
Measurement[] existing = measurements[index];
for (int i = 0; i < existing.length; i++) {
Measurement existingMeasurement = existing[i];
if (existingMeasurement == null) {
measurements[index][i] = measurement;
return;
}
if (equals(existingMeasurement.city, measurement.city)) {
existingMeasurement.merge(measurement);
return;
}
}
}
private static boolean equals(byte[] city1, byte[] city2) {
for (int i = 0; i < city1.length; i++) {
if (city1[i] != city2[i]) {
return false;
}
}
return true;
}
private record FileSegment(long start, long end) {
}
private static final class Measurement {
private int hash;
private byte[] city;
int min;
int max;
int sum;
int count;
private Measurement(int hash, byte[] city, int temp) {
this.hash = hash;
this.city = city;
this.min = this.max = this.sum = temp;
this.count = 1;
}
private void merge(Measurement m2) {
this.min = this.min < m2.min ? this.min : m2.min;
this.max = this.max > m2.max ? this.max : m2.max;
this.sum = this.sum + m2.sum;
this.count = this.count + m2.count;
}
@Override
public String toString() {
return String.format(
"%.1f/%.1f/%.1f", this.min / 10f, (this.sum / 10f) / this.count, this.max / 10f);
}
}
private static List<FileSegment> getFileSegments(final File file) throws IOException {
final int numberOfSegments = Runtime.getRuntime().availableProcessors() * 4;
final long fileSize = file.length();
final long segmentSize = fileSize / numberOfSegments;
if (segmentSize < 1000) {
return List.of(new FileSegment(0, fileSize));
}
try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r")) {
int lastSegment = numberOfSegments - 1;
return IntStream.range(0, numberOfSegments)
.mapToObj(
i -> {
long segStart = i * segmentSize;
long segEnd = (i == lastSegment) ? fileSize : segStart + segmentSize;
try {
segStart = findSegment(i, 0, randomAccessFile, segStart, segEnd);
segEnd = findSegment(i, lastSegment, randomAccessFile, segEnd, fileSize);
}
catch (IOException e) {
throw new RuntimeException(e);
}
return new FileSegment(segStart, segEnd);
})
.toList();
}
}
private static long findSegment(
final int i, final int skipSegment, RandomAccessFile raf, long location, final long fileSize)
throws IOException {
if (i != skipSegment) {
raf.seek(location);
while (location < fileSize) {
location++;
if (raf.read() == '\n')
return location;
}
}
return location;
}
}
|
