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
|
/*
* 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.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.lang.foreign.ValueLayout;
import java.nio.channels.FileChannel;
import java.util.*;
import java.util.concurrent.ForkJoinPool;
// Solution using project Panama and Map Reduce
public class CalculateAverage_MahmoudFawzyKhalil {
private static final String FILE = "./measurements.txt";
public static void main(String[] args) throws Exception {
mapReduce();
}
private static void mapReduce() throws IOException {
var f = new File(FILE);
try (var raf = new RandomAccessFile(f, "r")) {
FileChannel channel = raf.getChannel();
long fileSize = channel.size();
MemorySegment ms = channel.map(FileChannel.MapMode.READ_ONLY, 0, fileSize, Arena.global());
long chunkSize = fileSize / ForkJoinPool.commonPool().getParallelism();
List<Chunk> chunks = getChunks(ms, chunkSize);
Map<String, MeasurementAggregate> result = chunks.stream()
.parallel()
.map(c -> readChunkToMap(c, ms))
.reduce(Collections.emptyMap(), (a, b) -> combine(a, b));
System.out.println(new TreeMap<>(result));
}
}
private static List<Chunk> getChunks(MemorySegment ms, long chunkSize) {
List<Chunk> chunks = new ArrayList<>(32);
long start = 0;
long fileSize = ms.byteSize();
long end = chunkSize;
while (start < fileSize) {
byte b = ms.get(ValueLayout.JAVA_BYTE, end);
if (b == '\n') {
chunks.add(new Chunk(start, end));
start = end + 1;
end = Math.min(end + chunkSize, fileSize - 2);
}
end++;
}
return chunks;
}
private static Map<String, MeasurementAggregate> readChunkToMap(Chunk chunk, MemorySegment ms) {
Map<String, MeasurementAggregate> map = new HashMap<>();
long start = chunk.start();
while (start < chunk.end()) {
long cityNameSize = 0;
while (ms.get(ValueLayout.JAVA_BYTE, start + cityNameSize) != ';') {
cityNameSize++;
}
String cityName = readString(ms, start, cityNameSize);
start = start + cityNameSize + 1;
long temperatureSize = 0;
while (ms.get(ValueLayout.JAVA_BYTE, start + temperatureSize) != '\n') {
temperatureSize++;
}
String temperature = readString(ms, start, temperatureSize);
start = start + temperatureSize + 1;
// System.out.println(STR."\{cityName};\{temperature}");
addMeasurement(map, cityName, temperature);
}
return map;
}
// Credit goes to imrafaelmerino for combine function
private static Map<String, MeasurementAggregate> combine(Map<String, MeasurementAggregate> xs, Map<String, MeasurementAggregate> ys) {
Map<String, MeasurementAggregate> result = new HashMap<>();
for (var key : xs.keySet()) {
var m1 = xs.get(key);
var m2 = ys.get(key);
var combined = (m2 == null) ? m1 : (m1 == null) ? m2 : m1.combine(m2);
result.put(key, combined);
}
for (var key : ys.keySet())
result.putIfAbsent(key, ys.get(key));
return result;
}
private static String readString(MemorySegment ms, long start, long size) {
byte[] stringBytes = ms.asSlice(start, size)
.toArray(ValueLayout.JAVA_BYTE);
return new String(stringBytes);
}
private static void addMeasurement(Map<String, MeasurementAggregate> measurements, String station, String reading) {
measurements.compute(station,
(_, oldMeasurements) -> oldMeasurements == null ? MeasurementAggregate.of(reading) : oldMeasurements.update(reading));
}
record Chunk(long start, long end) {
}
private static final class MeasurementAggregate {
private double min;
private double max;
private double sum;
private long count;
private MeasurementAggregate(double min, double max, double sum, long count) {
this.min = min;
this.max = max;
this.sum = sum;
this.count = count;
}
public static MeasurementAggregate of(String temperature) {
double measurement = Double.parseDouble(temperature);
return new MeasurementAggregate(measurement, measurement, measurement, 1);
}
@Override
public boolean equals(Object obj) {
if (obj == this)
return true;
if (obj == null || obj.getClass() != this.getClass())
return false;
var that = (MeasurementAggregate) obj;
return Double.doubleToLongBits(this.min) == Double.doubleToLongBits(that.min) &&
Double.doubleToLongBits(this.max) == Double.doubleToLongBits(that.max) &&
Double.doubleToLongBits(this.sum) == Double.doubleToLongBits(that.sum) &&
this.count == that.count;
}
@Override
public int hashCode() {
return Objects.hash(min, max, sum, count);
}
public MeasurementAggregate update(String part) {
double measurement = Double.parseDouble(part);
this.min = Math.min(this.min, measurement);
this.max = Math.max(this.max, measurement);
this.sum += measurement;
this.count++;
return this;
}
public String toString() {
return min + "/" + round(round(sum) / count) + "/" + max;
}
private double round(double value) {
return Math.round(value * 10.0) / 10.0;
}
public MeasurementAggregate combine(MeasurementAggregate m2) {
return new MeasurementAggregate(
Math.min(this.min, m2.min),
Math.max(this.max, m2.max),
this.sum + m2.sum,
this.count + m2.count);
}
}
}
|
