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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.ByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.CompletionHandler;
import java.nio.charset.StandardCharsets;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedBlockingQueue;
/**
* Calculates the average using AIO and multiple threads.
*
* @author Xylitol
*/
public class CalculateAverage_C5H12O5 {
private static final int BUFFER_CAPACITY = 1024 * 1024 * 10;
private static final int MAP_CAPACITY = 10000;
private static final int PROCESSORS = Runtime.getRuntime().availableProcessors();
private static final BlockingQueue<byte[]> BYTES_QUEUE = new LinkedBlockingQueue<>(PROCESSORS);
private static long readPosition;
public static void main(String[] args) throws Exception {
System.out.println(calc("./measurements.txt"));
}
/**
* Calculate the average.
*/
public static String calc(String path) throws IOException, ExecutionException, InterruptedException {
readPosition = 0;
Map<String, MeasurementData> result = HashMap.newHashMap(MAP_CAPACITY);
// read and offer to queue
try (AsynchronousFileChannel channel = AsynchronousFileChannel.open(
Paths.get(path), Set.of(StandardOpenOption.READ), Executors.newVirtualThreadPerTaskExecutor())) {
ByteBuffer buffer = ByteBuffer.allocateDirect(BUFFER_CAPACITY);
channel.read(buffer, readPosition, buffer, new CompletionHandler<>() {
@Override
public void completed(Integer bytesRead, ByteBuffer buffer) {
try {
if (bytesRead > 0) {
for (int i = buffer.position() - 1; i >= 0; i--) {
if (buffer.get(i) == '\n') {
buffer.limit(i + 1);
break;
}
}
buffer.flip();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
readPosition += buffer.limit();
BYTES_QUEUE.put(bytes);
buffer.clear();
channel.read(buffer, readPosition, buffer, this);
}
else {
for (int i = 0; i < PROCESSORS; i++) {
BYTES_QUEUE.put(new byte[0]);
}
}
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
@Override
public void failed(Throwable exc, ByteBuffer buffer) {
// ignore
}
});
@SuppressWarnings("unchecked")
FutureTask<Map<MeasurementName, MeasurementData>>[] tasks = new FutureTask[PROCESSORS];
for (int i = 0; i < PROCESSORS; i++) {
tasks[i] = new FutureTask<>(new Task());
new Thread(tasks[i]).start();
}
for (FutureTask<Map<MeasurementName, MeasurementData>> task : tasks) {
task.get().forEach((k, v) -> result.merge(k.toString(), v, MeasurementData::merge));
}
}
return new TreeMap<>(result).toString();
}
/**
* The measurement name.
*/
private record MeasurementName(byte[] bytes, int length) {
@Override
public boolean equals(Object name) {
MeasurementName other = (MeasurementName) name;
if (other.length != length) {
return false;
}
return Arrays.compare(bytes, 0, length, other.bytes, 0, length) == 0;
}
@Override
public int hashCode() {
int result = 1;
for (int i = 0; i < length; i++) {
result = 31 * result + bytes[i];
}
return result;
}
@Override
public String toString() {
return new String(bytes, 0, length, StandardCharsets.UTF_8);
}
}
/**
* The measurement data.
*/
private static class MeasurementData {
private int min;
private int max;
private int sum;
private int count;
public MeasurementData(int value) {
this.min = value;
this.max = value;
this.sum = value;
this.count = 1;
}
public MeasurementData merge(MeasurementData data) {
return merge(data.min, data.max, data.sum, data.count);
}
public MeasurementData merge(int min, int max, int sum, int count) {
this.min = Math.min(this.min, min);
this.max = Math.max(this.max, max);
this.sum += sum;
this.count += count;
return this;
}
@Override
public String toString() {
return (min / 10.0) + "/" + (Math.round((double) sum / count) / 10.0) + "/" + (max / 10.0);
}
}
/**
* The task to calculate.
*/
private static class Task implements Callable<Map<MeasurementName, MeasurementData>> {
@Override
public Map<MeasurementName, MeasurementData> call() throws InterruptedException {
// poll from queue and calculate
Map<MeasurementName, MeasurementData> result = HashMap.newHashMap(MAP_CAPACITY);
for (byte[] bytes = BYTES_QUEUE.take(); true; bytes = BYTES_QUEUE.take()) {
if (bytes.length == 0) {
break;
}
int start = 0;
for (int end = 0; end < bytes.length; end++) {
if (bytes[end] == '\n') {
byte[] newBytes = new byte[end - start];
System.arraycopy(bytes, start, newBytes, 0, newBytes.length);
int semicolon = newBytes.length - 4;
for (; semicolon >= 0; semicolon--) {
if (newBytes[semicolon] == ';') {
break;
}
}
MeasurementName station = new MeasurementName(newBytes, semicolon);
int value = toInt(newBytes, semicolon + 1);
MeasurementData data = result.get(station);
if (data != null) {
data.merge(value, value, value, 1);
}
else {
result.put(station, new MeasurementData(value));
}
start = end + 1;
}
}
}
return result;
}
/**
* Convert the byte array to int.
*/
private static int toInt(byte[] bytes, int start) {
boolean negative = false;
int result = 0;
for (int i = start; i < bytes.length; i++) {
byte b = bytes[i];
if (b == '-') {
negative = true;
continue;
}
if (b != '.') {
result = result * 10 + (b - '0');
}
}
return negative ? -result : result;
}
}
}
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