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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.ByteBuffer;
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.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
public class CalculateAverage_AbstractKamen {
private static final String FILE = "./measurements.txt";
private static class Measurement {
private int min = Integer.MAX_VALUE;
private int max = Integer.MIN_VALUE;
private int sum;
private long count;
public String toString() {
return round(min / 10.0) + "/" + round(sum / 10.0 / count) + "/" + round(max / 10.0);
}
private double round(double value) {
return Math.round(value * 10.0) / 10.0;
}
}
public static void main(String[] args) throws IOException {
try (final FileChannel fc = FileChannel.open(Paths.get(FILE), StandardOpenOption.READ);
final RandomAccessFile raf = new RandomAccessFile(new File(FILE), "r")) {
final Map<String, Measurement> res = getParallelBufferStream(raf, fc)
.map(CalculateAverage_AbstractKamen::getMeasurements)
.flatMap(m -> m.entrySet().stream())
.collect(Collectors.collectingAndThen(
Collectors.toMap(Map.Entry::getKey,
Map.Entry::getValue,
CalculateAverage_AbstractKamen::aggregateMeasurements),
TreeMap::new));
System.out.println(res);
}
}
private static Measurement aggregateMeasurements(Measurement src, Measurement target) {
target.min = Math.min(src.min, target.min);
target.max = Math.max(src.max, target.max);
target.sum = src.sum + target.sum;
target.count = src.count + target.count;
return target;
}
private static Map<String, Measurement> getMeasurements(BufferSupplier getBuffer) {
final Map<String, Measurement> map = new HashMap<>(50_000);
final ByteBuffer byteBuffer = getBuffer.get();
final byte[] bytes = new byte[512];
while (byteBuffer.hasRemaining()) {
int nameLen = 0;
String name;
byte b;
while ((b = byteBuffer.get()) != ';') {
bytes[nameLen++] = b;
}
name = new String(bytes, 0, nameLen, StandardCharsets.UTF_8);
int valueLen = 0;
int neg = 1;
while (byteBuffer.hasRemaining() && ((b = byteBuffer.get()) != '\n')) {
if (b == '-') {
neg = -1;
}
else if (b == '.' || b == '\r') {
// skip the dot and retart char
}
else {
bytes[valueLen++] = b;
}
}
final int val = parseAsInt(valueLen, bytes);
takeMeasurement(val * neg, map, name);
}
return map;
}
private static int parseAsInt(int valueLen, byte[] bytes) {
int val;
switch (valueLen) {
case 2 -> val = (bytes[0] - 48) * 10 + (bytes[1] - 48);
case 3 -> val = (bytes[0] - 48) * 100 + (bytes[1] - 48) * 10 + (bytes[2] - 48);
default -> val = 0;
}
return val;
}
private static void takeMeasurement(int temperature, Map<String, Measurement> map, String name) {
Measurement measurement = map.get(name);
if (measurement != null) {
measurement.min = Math.min(measurement.min, temperature);
measurement.max = Math.max(measurement.max, temperature);
measurement.sum += temperature;
measurement.count++;
}
else {
measurement = new Measurement();
map.put(name, measurement);
measurement.min = temperature;
measurement.max = temperature;
measurement.sum = temperature;
measurement.count = 1;
}
}
private static Stream<BufferSupplier> getParallelBufferStream(RandomAccessFile raf, FileChannel fc) throws IOException {
final int availableProcessors = Runtime.getRuntime().availableProcessors();
return StreamSupport.stream(
StreamSupport.stream(
Spliterators.spliterator(
new BufferSupplierIterator(raf, fc, availableProcessors), availableProcessors,
Spliterator.IMMUTABLE | Spliterator.SIZED | Spliterator.SUBSIZED),
false)
.spliterator(),
true);
}
}
interface BufferSupplier extends Supplier<ByteBuffer> {
}
class BufferSupplierIterator implements Iterator<BufferSupplier> {
private long start;
private final RandomAccessFile raf;
private final FileChannel fc;
private final long fileLength;
private final long chunkSize;
public BufferSupplierIterator(RandomAccessFile raf, FileChannel fc, int numberOfParts) throws IOException {
this.raf = raf;
this.fc = fc;
this.fileLength = fc.size();
this.chunkSize = Math.min(fileLength / numberOfParts, 1073741824);
}
@Override
public boolean hasNext() {
return start < fileLength;
}
@Override
public BufferSupplier next() {
try {
if (hasNext()) {
final long end = getEnd();
long s = start;
this.start = end;
return getBufferSupplier(s, end);
}
else {
throw new NoSuchElementException();
}
}
catch (IOException e) {
throw new RuntimeException(e);
}
}
private long getEnd() throws IOException {
long end = Math.min(start + chunkSize, fileLength);
while (end < fileLength) {
raf.seek(end++);
if (raf.read() == '\n')
break;
}
return end;
}
private BufferSupplier getBufferSupplier(long position, long end) {
final long size = end - position;
return new BufferSupplier() {
private ByteBuffer bb;
@Override
public ByteBuffer get() {
try {
if (bb == null) {
return (bb = fc.map(MapMode.READ_ONLY, position, size));
}
else {
return bb;
}
}
catch (IOException e) {
throw new RuntimeException(e);
}
}
};
}
}
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