Adding Peter Lawrey's submission
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Peter Lawrey
GitHub
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calculate_average_lawrey.sh
Executable file
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calculate_average_lawrey.sh
Executable file
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#!/bin/sh
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#
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# Copyright 2023 The original authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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JAVA_OPTS=""
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time java $JAVA_OPTS -verbose:gc -Xmx99m --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_lawrey
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215
src/main/java/dev/morling/onebrc/CalculateAverage_lawrey.java
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src/main/java/dev/morling/onebrc/CalculateAverage_lawrey.java
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/*
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* Copyright 2023 The original authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dev.morling.onebrc;
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import java.io.File;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.nio.MappedByteBuffer;
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import java.nio.channels.FileChannel;
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import java.nio.charset.StandardCharsets;
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import java.util.*;
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import java.util.stream.LongStream;
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public class CalculateAverage_lawrey {
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// Path to the file containing temperature measurements.
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private static final String FILE = "./measurements.txt";
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// Inner class representing a measurement with min, max, and average calculations.
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static class Measurement {
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double min = Double.POSITIVE_INFINITY;
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double max = Double.NEGATIVE_INFINITY;
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double sum = 0.0;
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long count = 0;
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// Default constructor for Measurement.
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public Measurement() {
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}
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// Adds a new temperature sample and updates min, max, and average.
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public void sample(double temp) {
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min = Math.min(min, temp);
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max = Math.max(max, temp);
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sum += temp;
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count++;
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}
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// Returns a formatted string representing min, average, and max.
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public String toString() {
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return round(min) + "/" + round(sum / count) + "/" + round(max);
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}
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// Helper method to round a double value to one decimal place.
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private double round(double value) {
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return Math.round(value * 10.0) / 10.0;
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}
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// Merges this Measurement with another Measurement.
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public Measurement merge(Measurement m2) {
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min = Math.min(min, m2.min);
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max = Math.max(max, m2.max);
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sum += m2.sum;
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count += m2.count;
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return this;
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}
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}
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// Inner class representing a key for measurements.
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static class Key {
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final byte[] data = new byte[32];
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int hash = 0, length = 0;
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// Override of hashCode using the hash field.
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@Override
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public int hashCode() {
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return hash;
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}
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// Custom equals method to compare two Key objects.
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@Override
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public boolean equals(Object obj) {
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if (obj instanceof Key k) {
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if (length != k.length || hash != k.hash)
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return false;
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return Arrays.equals(data, 0, length, k.data, 0, length);
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}
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return false;
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}
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// Converts the key's data to a String.
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@Override
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public String toString() {
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return new String(data, 0, length, StandardCharsets.UTF_8);
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}
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// Appends a byte to the key and updates its hash.
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public void append(byte b) {
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data[length++] = b;
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hash = hash * 10191 + b;
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}
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// Resets the key to its initial state.
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public void clear() {
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length = hash = 0;
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}
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}
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public static void main(String[] args) throws IOException {
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// Open the file for reading.
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File file = new File(FILE);
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long length = file.length();
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long chunk = 1 << 28; // Size of the chunk to be processed.
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RandomAccessFile raf = new RandomAccessFile(file, "r");
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// Process the file in chunks and merge the results.
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Map<Key, Measurement> allMeasurementsMap = LongStream.range(0, length / chunk + 1)
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.parallel()
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.mapToObj(i -> extractMeasurementsFromChunk(i, chunk, length, raf))
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.reduce((a, b) -> mergeMeasurementMaps(a, b))
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.orElseGet(Collections::emptyMap);
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// Sort the measurements and print them.
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Map<String, Measurement> sortedMeasurementsMap = new TreeMap<>();
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allMeasurementsMap.forEach((k, m) -> sortedMeasurementsMap.put(k.toString(), m));
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System.out.println(sortedMeasurementsMap);
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}
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// Merges two measurement maps.
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private static Map<Key, Measurement> mergeMeasurementMaps(Map<Key, Measurement> a, Map<Key, Measurement> b) {
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a.forEach((k, m) -> {
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Measurement m2 = b.get(k);
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if (m2 != null)
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m.merge(m2);
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});
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b.forEach(a::putIfAbsent);
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return a;
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}
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// Extracts measurements from a chunk of the file.
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private static Map<Key, Measurement> extractMeasurementsFromChunk(long i, long chunk, long length, RandomAccessFile raf) {
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long start = i * chunk;
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long size = Math.min(length, start + chunk + 64 * 1024) - start;
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Map<Key, Measurement> map = new HashMap<>(1024);
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try {
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MappedByteBuffer mbb = raf.getChannel().map(FileChannel.MapMode.READ_ONLY, start, size);
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if (i > 0)
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skipToFirstLine(mbb);
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Key key = new Key();
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while (mbb.remaining() > 0 && mbb.position() <= chunk) {
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key.clear();
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readKey(mbb, key);
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int temp = readTemperatureFromBuffer(mbb);
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Measurement m = map.computeIfAbsent(key, n -> new Measurement());
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if (m.count == 0)
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key = new Key();
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m.sample(temp / 10.0);
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}
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} catch (IOException ioe) {
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throw new RuntimeException(ioe);
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}
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return map;
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}
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// Reads a temperature value from the buffer.
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private static int readTemperatureFromBuffer(MappedByteBuffer mbb) {
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int temp = 0;
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boolean negative = false;
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outer:
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while (mbb.remaining() > 0) {
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byte b = mbb.get();
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switch (b) {
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case '-':
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negative = true;
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break;
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case '.':
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break;
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case '\r':
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case '\n':
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break outer;
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default:
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temp = 10 * temp + (b - '0');
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break;
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}
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}
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if (mbb.remaining() > 0) {
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byte b = mbb.get(mbb.position());
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if (b == '\n')
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mbb.get();
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}
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if (negative)
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temp = -temp;
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return temp;
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}
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// Reads a key from the buffer.
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private static void readKey(MappedByteBuffer mbb, Key key) {
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while (mbb.remaining() > 0) {
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byte b = mbb.get();
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if (b == ';' || b == '\r' || b == '\n')
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break;
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key.append(b);
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}
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}
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// Skips to the first line in the buffer, used for chunk processing.
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private static void skipToFirstLine(MappedByteBuffer mbb) {
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while ((mbb.get() & 0xFF) >= ' ') {
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// Skip bytes until reaching the start of a line.
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}
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}
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}
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