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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.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.lang.foreign.ValueLayout;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
public class CalculateAverage_omarchenko4j {
private static final String FILE = "./measurements.txt";
private static final int NUMBER_OF_CORES = Runtime.getRuntime().availableProcessors();
private static final int MAX_LINE_SIZE = 128;
public static void main(String[] args) throws IOException, InterruptedException, ExecutionException {
try (var file = FileChannel.open(Paths.get(FILE), StandardOpenOption.READ)) {
var fileSize = file.size();
try (var arena = Arena.ofShared()) {
var segment = file.map(MapMode.READ_ONLY, 0, fileSize, arena);
var tasks = sliceIntoTasks(segment);
try (var executor = Executors.newFixedThreadPool(Math.min(tasks.size(), NUMBER_OF_CORES))) {
var futures = executor.invokeAll(tasks);
var measurements = new TreeMap<String, Aggregator>(String::compareTo);
for (var future : futures) {
var result = future.get();
for (var entry : result.entrySet()) {
var station = entry.getKey();
var a1 = entry.getValue();
var a2 = measurements.get(station);
if (a2 != null) {
a1.merge(a2);
}
measurements.put(station, a1);
}
}
System.out.println(measurements);
}
}
}
}
private static List<Task> sliceIntoTasks(MemorySegment segment) {
var tasks = new ArrayList<Task>(NUMBER_OF_CORES);
var segmentSize = segment.byteSize();
var chunkSize = segmentSize / NUMBER_OF_CORES;
if (chunkSize < (long) NUMBER_OF_CORES * MAX_LINE_SIZE) {
return List.of(new Task(segment, 0, segmentSize));
}
long offsetStart = 0;
for (int coreNumber = 1; coreNumber <= NUMBER_OF_CORES; coreNumber++) {
long offsetEnd = chunkSize * coreNumber;
while (offsetEnd < segmentSize) {
var b = segment.get(ValueLayout.JAVA_BYTE, offsetEnd);
offsetEnd++;
if (b == '\n') {
break;
}
}
tasks.add(new Task(segment, offsetStart, offsetEnd));
offsetStart = offsetEnd;
}
return tasks;
}
private static class Task implements Callable<Map<String, Aggregator>> {
private static final byte SEPARATOR = ';';
private static final byte END_LINE = '\n';
private final MemorySegment segment;
private final long startOffset;
private final long endOffset;
private Task(MemorySegment segment, long startOffset, long endOffset) {
this.segment = segment;
this.startOffset = startOffset;
this.endOffset = endOffset;
}
@Override
public Map<String, Aggregator> call() {
var measurements = new HashMap<String, Aggregator>(512);
int startIndex = 0;
int separatorIndex = 0;
int endIndex = 0;
var buffer = new byte[MAX_LINE_SIZE];
int bufferIndex = 0;
for (long offset = startOffset; offset < endOffset; offset++) {
var b = segment.get(ValueLayout.JAVA_BYTE, offset);
buffer[bufferIndex] = b;
bufferIndex++;
if (b == SEPARATOR) {
separatorIndex = bufferIndex - 1;
continue;
}
if (b == END_LINE) {
endIndex = bufferIndex - 1;
var station = new String(buffer, startIndex, separatorIndex);
var value = getDouble(buffer, separatorIndex + 1, endIndex - separatorIndex - 1);
measurements.computeIfAbsent(station, ignored -> new Aggregator()).addValue(value);
bufferIndex = 0;
}
}
return measurements;
}
private static final byte MINUS = '-';
private static final byte ZERO = '0';
private double getDouble(byte[] buffer, int offset, int length) {
if (length == 4) {
if (buffer[offset] == MINUS) {
int value;
value = buffer[offset + 1] - ZERO;
value = (value * 10) + (buffer[offset + 3] - ZERO);
value = -value;
return value * .1D;
}
int value;
value = buffer[offset] - ZERO;
value = (value * 10) + (buffer[offset + 1] - ZERO);
value = (value * 10) + (buffer[offset + 3] - ZERO);
return value * .1D;
}
if (length == 3) {
int value;
value = buffer[offset] - ZERO;
value = (value * 10) + (buffer[offset + 2] - ZERO);
return value * .1D;
}
int value;
value = buffer[offset + 1] - ZERO;
value = (value * 10) + (buffer[offset + 2] - ZERO);
value = (value * 10) + (buffer[offset + 4] - ZERO);
value = -value;
return value * .1D;
}
}
public static class Aggregator {
private double min = Double.POSITIVE_INFINITY;
private double max = Double.NEGATIVE_INFINITY;
private double sum;
private long count;
public void addValue(double value) {
min = Math.min(min, value);
max = Math.max(max, value);
sum += value;
count++;
}
public void merge(Aggregator aggregator) {
if (aggregator.min < min) {
min = aggregator.min;
}
if (aggregator.max > max) {
max = aggregator.max;
}
sum += aggregator.sum;
count += aggregator.count;
}
@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;
}
}
}
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