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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.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.*;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.stream.Collectors;
public class CalculateAverage_zerninv {
private static final String FILE = "./measurements.txt";
private static final int MIN_FILE_SIZE = 1024 * 1024;
private static final char DELIMITER = ';';
private static final char LINE_SEPARATOR = '\n';
private static final char ZERO = '0';
private static final char NINE = '9';
private static final char MINUS = '-';
public static void main(String[] args) throws IOException {
var results = new HashMap<String, MeasurementAggregation>();
try (var channel = FileChannel.open(Path.of(FILE), StandardOpenOption.READ)) {
var fileSize = channel.size();
var cores = Runtime.getRuntime().availableProcessors();
var chunks = cores - 1;
var maxChunkSize = fileSize < MIN_FILE_SIZE ? fileSize : Math.min(fileSize / chunks, Integer.MAX_VALUE);
var chunkOffsets = splitByChunks(channel, maxChunkSize);
var executor = Executors.newFixedThreadPool(cores);
List<Future<Map<String, MeasurementAggregation>>> fResults = new ArrayList<>();
for (int i = 1; i < chunkOffsets.size(); i++) {
final long prev = chunkOffsets.get(i - 1);
final long curr = chunkOffsets.get(i);
fResults.add(executor.submit(() -> calcForChunk(channel, prev, curr)));
}
fResults.forEach(f -> {
try {
f.get().forEach((key, value) -> {
var result = results.get(key);
if (result != null) {
result.merge(value);
}
else {
results.put(key, value);
}
});
}
catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
});
executor.shutdown();
}
System.out.println(new TreeMap<>(results));
}
private static List<Long> splitByChunks(FileChannel channel, long maxChunkSize) throws IOException {
long size = channel.size();
List<Long> result = new ArrayList<>();
long current = 0;
result.add(current);
while (current < size) {
var mbb = channel.map(FileChannel.MapMode.READ_ONLY, current, Math.min(size - current, maxChunkSize));
int position = mbb.limit() - 1;
while (mbb.get(position) != LINE_SEPARATOR) {
position--;
}
current += position + 1;
result.add(current);
}
return result;
}
private static Map<String, MeasurementAggregation> calcForChunk(FileChannel channel, long begin, long end) throws IOException {
var results = new HashMap<CityWrapper, MeasurementAggregation>(10_000);
var mbb = channel.map(FileChannel.MapMode.READ_ONLY, begin, end - begin);
int cityOffset, hashCode, temperatureOffset, temperature;
byte b;
while (mbb.hasRemaining()) {
cityOffset = mbb.position();
hashCode = 0;
while ((b = mbb.get()) != DELIMITER) {
hashCode = 31 * hashCode + b;
}
temperatureOffset = mbb.position();
CityWrapper city = new CityWrapper(mbb, cityOffset, temperatureOffset - cityOffset - 1, hashCode);
temperature = 0;
while ((b = mbb.get()) != LINE_SEPARATOR) {
if (b >= ZERO && b <= NINE) {
temperature = temperature * 10 + (b - ZERO);
}
}
if (mbb.get(temperatureOffset) == MINUS) {
temperature *= -1;
}
var result = results.get(city);
if (result != null) {
result.addTemperature(temperature);
}
else {
results.put(city, new MeasurementAggregation().addTemperature(temperature));
}
}
return results.entrySet()
.stream()
.collect(Collectors.toMap(entry -> entry.getKey().toString(), Map.Entry::getValue));
}
private static final class MeasurementAggregation {
private long sum;
private int count;
private int min = Integer.MAX_VALUE;
private int max = Integer.MIN_VALUE;
public MeasurementAggregation addTemperature(int temperature) {
sum += temperature;
count++;
min = Math.min(temperature, min);
max = Math.max(temperature, max);
return this;
}
public void merge(MeasurementAggregation o) {
if (o == null) {
return;
}
sum += o.sum;
count += o.count;
min = Math.min(min, o.min);
max = Math.max(max, o.max);
}
@Override
public String toString() {
return String.format("%.1f/%.1f/%.1f", min / 10d, sum / 10d / count, max / 10d);
}
}
private record CityWrapper(MappedByteBuffer mbb, int begin, int size, int hash) {
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
CityWrapper that = (CityWrapper) o;
if (hash != that.hash || size != that.size) {
return false;
}
for (int i = 0; i < size; i++) {
if (mbb.get(begin + i) != mbb.get(that.begin + i)) {
return false;
}
}
return true;
}
@Override
public int hashCode() {
return hash;
}
@Override
public String toString() {
byte[] arr = new byte[size];
for (int i = 0; i < size; i++) {
arr[i] = mbb.get(begin + i);
}
return new String(arr);
}
}
}
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