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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.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.nio.charset.StandardCharsets;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.*;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class CalculateAverage_maximz101 {
private static final String FILE = "./measurements.txt";
private record Measurement(String station, double value) {
}
private record ResultRow(double min, double mean, double max) {
public String toString() {
return STR."\{round(min)}/\{round(mean)}/\{round(max)}";
}
private double round(double value) {
return Math.round(value * 10.0) / 10.0;
}
}
private static class MeasurementAggregator {
private double min;
private double max;
private double sum;
private long count;
public MeasurementAggregator(double min, double max, double sum, long count) {
this.min = min;
this.max = max;
this.sum = sum;
this.count = count;
}
}
record FileChunkRange(long start, long end) {
}
public static void main(String[] args) throws IOException {
int parallelism = args.length == 1 ? Integer.parseInt(args[0]) : Runtime.getRuntime().availableProcessors();
Map<String, ResultRow> measurements = new ConcurrentHashMap<>();
try (ExecutorService executor = Executors.newWorkStealingPool(parallelism)) {
List<FileChunkRange> chunks = getChunks(new File(FILE), parallelism, 1_048_576);
List<CompletableFuture<Void>> completableFutureList = new ArrayList<>();
for (FileChunkRange chunk : chunks) {
completableFutureList
.add(CompletableFuture
.supplyAsync(() -> computePartialAggregations(chunk), executor)
.thenAccept(map -> updateResultMap(map, measurements)));
}
CompletableFuture.allOf(completableFutureList.toArray(new CompletableFuture[0]))
.thenAccept(_ -> System.out.println(new TreeMap<>(measurements)))
.join();
}
}
private static void updateResultMap(Map<String, MeasurementAggregator> map, Map<String, ResultRow> measurements) {
map.forEach((station, agg) -> measurements.merge(station,
new ResultRow(agg.min, agg.sum / agg.count, agg.max),
(r1, r2) -> new ResultRow(Math.min(r1.min, r2.min), (r1.mean + r2.mean) / 2, Math.max(r1.max, r2.max))));
}
private static Map<String, MeasurementAggregator> computePartialAggregations(FileChunkRange chunk) {
try (FileChannel channel = FileChannel.open(Paths.get(FILE), StandardOpenOption.READ)) {
MappedByteBuffer buffer = channel.map(MapMode.READ_ONLY, chunk.start(), chunk.end() - chunk.start());
return process(buffer);
}
catch (IOException e) {
throw new RuntimeException(e);
}
}
private static List<FileChunkRange> getChunks(File file, int chunksCount, int minChunkSize) {
long fileSize = file.length();
long chunkSize = fileSize / chunksCount;
if (chunkSize < minChunkSize || chunksCount == 1) {
return List.of(new FileChunkRange(0, fileSize));
}
int currentChunk = 1;
long currentChunkStart = 0;
long currentChunkEnd = chunkSize;
var list = new ArrayList<FileChunkRange>(chunksCount);
try (RandomAccessFile raf = new RandomAccessFile(file, "r")) {
while (currentChunk <= chunksCount) {
currentChunkEnd = findNextEOLFrom(raf, currentChunkEnd);
list.add(new FileChunkRange(currentChunkStart, currentChunkEnd));
// next
currentChunkStart = currentChunkEnd + 1;
currentChunkEnd = currentChunkStart + chunkSize;
if (currentChunkEnd >= fileSize) {
list.add(new FileChunkRange(currentChunkStart, fileSize));
break;
}
currentChunk++;
}
}
catch (IOException e) {
throw new RuntimeException(e);
}
return list;
}
private static long findNextEOLFrom(RandomAccessFile raf, long currentChunkEnd) throws IOException {
raf.seek(currentChunkEnd);
while (currentChunkEnd < raf.length() && raf.read() != '\n') {
currentChunkEnd++;
}
return currentChunkEnd;
}
private static Map<String, MeasurementAggregator> process(MappedByteBuffer buffer) {
var map = new HashMap<String, MeasurementAggregator>();
byte[] lineBytes = new byte[107];
while (buffer.hasRemaining()) {
int i = 0;
lineBytes[i] = buffer.get();
int separatorIdx = -1;
while (lineBytes[i] != '\n' && buffer.hasRemaining()) {
lineBytes[++i] = buffer.get();
if (lineBytes[i] == ';') {
separatorIdx = i;
}
}
Measurement measurement = parseLine(lineBytes, separatorIdx, i);
map.merge(measurement.station,
new MeasurementAggregator(measurement.value, measurement.value, measurement.value, 1),
(agg, m) -> {
agg.min = Math.min(agg.min, m.min);
agg.max = Math.max(agg.max, m.max);
agg.sum += m.sum;
agg.count++;
return agg;
});
}
return map;
}
private static Measurement parseLine(byte[] lineBytes, int separatorIdx, int eolIdx) {
return new Measurement(
new String(lineBytes, 0, separatorIdx, StandardCharsets.UTF_8),
bytesToDouble(lineBytes, separatorIdx + 1, eolIdx));
}
private static double bytesToDouble(byte[] bytes, int startIdx, int endIdx) {
double d = 0d;
boolean negative = bytes[startIdx] == '-';
int numberStartIdx = negative ? 1 + startIdx : startIdx;
boolean afterDot = false;
int dots = 1;
for (int i = numberStartIdx; i < endIdx; i++) {
if (bytes[i] == '.') {
afterDot = true;
continue;
}
double n = bytes[i] - '0';
if (afterDot) {
d = d + n / Math.pow(10, dots++);
}
else {
d = d * Math.pow(10, i - numberStartIdx) + n;
}
}
return negative ? -d : d;
}
}
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