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Adding filiphr's submission;

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* Initial implementation using Shenandoah GC and parallel iteration

* Use memory mapped files

* Iterate the buffer once and use BigDecimal parsing instead of Double.parseDouble

* Add information about Graal

* Add sdk use to calculate script
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Filip Hrisafov 2024-01-03 20:32:16 +01:00 committed by GitHub
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commit d57cf78faa
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calculate_average_filiphr.sh Executable file
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#!/bin/sh
#
# 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.
#
sdk use java 21.0.1-graal
java -version
JAVA_OPTS=""
time java $JAVA_OPTS --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_filiphr

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src/main/java/dev/morling/onebrc/CalculateAverage_filiphr.java Normal file
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/*
* 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.IOException;
import java.io.UncheckedIOException;
import java.math.BigDecimal;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.TreeMap;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* Initial submission: 1m 35s
* Adding memory mapped files: 0m 55s (based on bjhara's submission)
* Using big decimal and iterating the buffer once: 0m 20s
* <p>
* Using 21.0.1 Temurin with ShenandoahGC on Macbook (Intel) Pro
* `sdk use java 21.0.1-tem`
*
* When using Oracle GraalVM 21.0.1+12.1
* `sdk use java 21.0.1-graal`
* It takes 0m 15s on my machine
* `sdk use java 21.0.1-graalce`
* It takes 0m 20s on my machine
*
* @author Filip Hrisafov
*/
public class CalculateAverage_filiphr {
private static final String FILE = "./measurements.txt";
private static final long CHUNK_SIZE = 1024 * 1024 * 10L; // 1KB * 10KB ~ 10MB
private static final class Measurement {
private double min = Long.MAX_VALUE;
private double max = Long.MIN_VALUE;
private double sum = 0L;
private long count = 0L;
private void add(double value) {
this.min = Math.min(this.min, value);
this.max = Math.max(this.max, value);
this.sum += value;
this.count++;
}
public static Measurement combine(Measurement m1, Measurement m2) {
Measurement measurement = new Measurement();
measurement.min = Math.min(m1.min, m2.min);
measurement.max = Math.max(m1.max, m2.max);
measurement.sum = m1.sum + m2.sum;
measurement.count = m1.count + m2.count;
return measurement;
}
@Override
public String toString() {
return round(min) + "/" + round((sum) / count) + "/" + round(max);
}
private double round(double value) {
return Math.round(value * 10.0) / 10.0;
}
}
public static void main(String[] args) throws IOException {
// long start = System.nanoTime();
Map<String, Measurement> measurements;
try (FileChannel fileChannel = FileChannel.open(Paths.get(FILE), StandardOpenOption.READ)) {
measurements = fineChannelStream(fileChannel)
.parallel()
.map(CalculateAverage_filiphr::parseBuffer)
.reduce(Collections.emptyMap(), CalculateAverage_filiphr::mergeMaps);
}
System.out.println(new TreeMap<>(measurements));
// System.out.println("Done in " + (System.nanoTime() - start) / 1000000 + " ms");
}
private static Map<String, Measurement> mergeMaps(Map<String, Measurement> map1, Map<String, Measurement> map2) {
if (map1.isEmpty()) {
return map2;
}
else {
Set<String> cities = new HashSet<>(map1.keySet());
cities.addAll(map2.keySet());
Map<String, Measurement> result = HashMap.newHashMap(cities.size());
for (String city : cities) {
Measurement m1 = map1.get(city);
Measurement m2 = map2.get(city);
if (m2 == null) {
// When m2 is null then it is not possible for m1 to be null as well,
// since cities is a union of the map key sets
result.put(city, m1);
}
else if (m1 == null) {
// When m1 is null then it is not possible for m2 to be null as well,
// since cities is a union of the map key sets
result.put(city, m2);
}
else {
result.put(city, Measurement.combine(m1, m2));
}
}
return result;
}
}
/**
* This is an adapted implementation of the bjhara parseBuffer
*/
private static Map<String, Measurement> parseBuffer(ByteBuffer bb) {
Map<String, Measurement> measurements = HashMap.newHashMap(415);
int limit = bb.limit();
byte[] buffer = new byte[128];
CharBuffer charBuffer = CharBuffer.allocate(8);
while (bb.position() < limit) {
int bufferIndex = 0;
// Iterate through the byte buffer and fill the buffer until we find the separator (;)
while (bb.position() < limit) {
byte positionByte = bb.get();
if (positionByte == ';') {
break;
}
buffer[bufferIndex++] = positionByte;
}
// Create the city
String city = new String(buffer, 0, bufferIndex);
charBuffer.clear();
byte lastPositionByte = '\n';
while (bb.position() < limit) {
byte positionByte = bb.get();
if (positionByte == '\r' || positionByte == '\n') {
lastPositionByte = positionByte;
break;
}
charBuffer.append((char) positionByte);
}
int position = charBuffer.position();
charBuffer.position(0);
// Create the temperature string
BigDecimal bigDecimal = new BigDecimal(charBuffer.array(), 0, position);
double value = bigDecimal.doubleValue();
measurements.computeIfAbsent(city, k -> new Measurement())
.add(value);
// and get rid of the new line (handle both kinds)
if (lastPositionByte == '\r') {
bb.get();
}
}
return measurements;
}
/**
* Thanks to bjhara and royvanrijn for the idea of using (and learning about) memory mapped files.
*/
private static Stream<ByteBuffer> fineChannelStream(FileChannel fileChannel) throws IOException {
return StreamSupport.stream(Spliterators.spliteratorUnknownSize(fileChannelIterator(fileChannel), Spliterator.IMMUTABLE), false);
}
private static Iterator<ByteBuffer> fileChannelIterator(FileChannel fileChannel) throws IOException {
return new Iterator<>() {
private final long size = fileChannel.size();
private long start = 0;
@Override
public boolean hasNext() {
return start < size;
}
@Override
public ByteBuffer next() {
try {
MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, start,
Math.min(CHUNK_SIZE, size - start));
// don't split the data in the middle of lines
// find the closest previous newline
int realEnd = mappedByteBuffer.limit() - 1;
while (mappedByteBuffer.get(realEnd) != '\n')
realEnd--;
realEnd++;
mappedByteBuffer.limit(realEnd);
start += realEnd;
return mappedByteBuffer;
}
catch (IOException ex) {
throw new UncheckedIOException(ex);
}
}
};
}
}