/*
* 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.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
public class CalculateAverage_gnabyl {
private static final String FILE = "./measurements.txt";
private static final int NB_CHUNKS = 8;
private static record Chunk(long start, int bytesCount, MappedByteBuffer mappedByteBuffer) {
}
private static int reduceSizeToFitLineBreak(FileChannel channel, long startPosition, int startSize)
throws IOException {
long currentPosition = startPosition + startSize - 1;
int realSize = startSize;
if (currentPosition >= channel.size()) {
currentPosition = channel.size() - 1;
realSize = (int) (currentPosition - startPosition);
}
while (currentPosition >= startPosition) {
channel.position(currentPosition);
byte byteValue = channel.map(FileChannel.MapMode.READ_ONLY, currentPosition, 1).get();
if (byteValue == '\n') {
// found line break
break;
}
realSize--;
currentPosition--;
}
return realSize;
}
private static List<Chunk> readChunks(long nbChunks) throws IOException {
RandomAccessFile file = new RandomAccessFile(FILE, "rw");
List<Chunk> res = new ArrayList<>();
FileChannel channel = file.getChannel();
long bytesCount = channel.size();
long bytesPerChunk = bytesCount / nbChunks;
// Memory map the file in read-only mode
// TODO: Optimize using threads
long currentPosition = 0;
for (int i = 0; i < nbChunks; i++) {
int startSize = (int) bytesPerChunk;
int realSize = startSize;
if (i == nbChunks - 1) {
realSize = (int) (bytesCount - currentPosition);
MappedByteBuffer mappedByteBuffer = channel.map(FileChannel.MapMode.READ_ONLY, currentPosition,
realSize);
res.add(new Chunk(currentPosition, realSize, mappedByteBuffer));
break;
}
// Adjust size so that it ends on a newline
realSize = reduceSizeToFitLineBreak(channel, currentPosition, startSize);
MappedByteBuffer mappedByteBuffer = channel.map(FileChannel.MapMode.READ_ONLY, currentPosition,
realSize);
res.add(new Chunk(currentPosition, realSize, mappedByteBuffer));
currentPosition += realSize;
}
channel.close();
file.close();
return res;
}
private static class StationData {
private double sum, min, max;
private long count;
public StationData(double value) {
this.count = 1;
this.sum = value;
this.min = value;
this.max = value;
}
public void update(double value) {
this.count++;
this.sum += value;
this.min = Math.min(this.min, value);
this.max = Math.max(this.max, value);
}
public double getMean() {
return sum / count;
}
public double getMin() {
return min;
}
public double getMax() {
return max;
}
public void mergeWith(StationData other) {
this.sum += other.sum;
this.count += other.count;
this.min = Math.min(this.min, other.min);
this.max = Math.max(this.max, other.max);
}
}
static double round(double value) {
return Math.round(value * 10.0) / 10.0;
}
private static class ChunkResult {
private Map<String, StationData> data;
public ChunkResult() {
data = new HashMap<>();
}
public StationData getData(String name) {
return data.get(name);
}
public void addStation(String name, double value) {
this.data.put(name, new StationData(value));
}
public void print() {
var stationNames = new ArrayList<String>(this.data.keySet());
Collections.sort(stationNames);
System.out.print("{");
for (int i = 0; i < stationNames.size() - 1; i++) {
var name = stationNames.get(i);
var stationData = data.get(name);
System.out.printf("%s=%.1f/%.1f/%.1f, ", name, round(stationData.getMin()),
round(stationData.getMean()),
round(stationData.getMax()));
}
var name = stationNames.get(stationNames.size() - 1);
var stationData = data.get(name);
System.out.printf("%s=%.1f/%.1f/%.1f", name, round(stationData.getMin()),
round(stationData.getMean()),
round(stationData.getMax()));
System.out.println("}");
}
public void mergeWith(ChunkResult other) {
for (Map.Entry<String, StationData> entry : other.data.entrySet()) {
String stationName = entry.getKey();
StationData otherStationData = entry.getValue();
StationData thisStationData = this.data.get(stationName);
if (thisStationData == null) {
this.data.put(stationName, otherStationData);
}
else {
thisStationData.mergeWith(otherStationData);
}
}
}
}
private static ChunkResult processChunk(Chunk chunk) {
ChunkResult result = new ChunkResult();
// Perform processing on the chunk data
byte[] data = new byte[chunk.bytesCount()];
chunk.mappedByteBuffer().get(data);
// Process each line
String stationName;
double value;
int iSplit, iEol;
StationData stationData;
long negative;
for (int offset = 0; offset < data.length; offset++) {
// Find station name
for (iSplit = offset; data[iSplit] != ';'; iSplit++) {
}
stationName = new String(data, offset, iSplit - offset, StandardCharsets.UTF_8);
// Find value
iSplit++;
negative = 1;
value = 0;
for (iEol = iSplit; data[iEol] != '\n'; iEol++) {
if (data[iEol] == '-') {
negative = -1;
continue;
}
if (data[iEol] == '.') {
value = value + (data[iEol + 1] - 48) / 10.0;
iEol += 2;
break;
}
value = value * 10 + data[iEol] - 48;
}
value *= negative;
// Init & count
stationData = result.getData(stationName);
if (stationData == null) {
result.addStation(stationName, value);
}
else {
stationData.update(value);
}
offset = iEol;
}
return result;
}
private static ChunkResult processAllChunks(List<Chunk> chunks) throws InterruptedException, ExecutionException {
// var globalRes = new ChunkResult();
// for (var chunk : chunks) {
// var chunkRes = processChunk(chunk);
// globalRes.mergeWith(chunkRes);
// }
// return globalRes;
List<CompletableFuture<ChunkResult>> computeTasks = new ArrayList<>();
for (Chunk chunk : chunks) {
computeTasks.add(CompletableFuture.supplyAsync(() -> processChunk(chunk)));
}
ChunkResult globalRes = null;
for (CompletableFuture<ChunkResult> completedTask : computeTasks) {
ChunkResult chunkRes = completedTask.get();
if (globalRes == null) {
globalRes = completedTask.get();
}
else {
globalRes.mergeWith(chunkRes);
}
}
return globalRes;
}
public static void main(String[] args) throws IOException, InterruptedException, ExecutionException {
var chunks = readChunks(NB_CHUNKS);
var result = processAllChunks(chunks);
result.print();
}
}