2024-01-03 10:14:19 +01:00
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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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2024-01-03 19:14:15 +01:00
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2024-01-03 14:53:38 +01:00
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import java.io.*;
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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.nio.file.Files;
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import java.nio.file.Path;
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import java.nio.file.StandardOpenOption;
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import java.time.Duration;
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import java.time.Instant;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.TreeMap;
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// gunnar morling - 2:10
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// roy van rijn - 1:01
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2024-01-03 14:53:38 +01:00
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// 0:37
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public class CalculateAverage_ddimtirov {
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private static final String FILE = "./measurements.txt";
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private static final int HASH_NO_CLASH_MODULUS = 49999;
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private static final int OFFSET_MIN = 0;
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private static final int OFFSET_MAX = 1;
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private static final int OFFSET_COUNT = 2;
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@SuppressWarnings("RedundantSuppression")
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public static void main(String[] args) throws IOException {
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var path = Path.of(FILE);
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var start = Instant.now();
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var desiredSegmentsCount = Runtime.getRuntime().availableProcessors();
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var segments = FileSegment.forFile(path, desiredSegmentsCount);
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var trackers = segments.stream().parallel().map(segment -> {
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try (var fileChannel = (FileChannel) Files.newByteChannel(path, StandardOpenOption.READ)) {
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var tracker = new Tracker();
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var segmentBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, segment.start(), segment.size());
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tracker.processSegment(segmentBuffer, segment.end());
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return tracker;
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} catch (IOException e) {
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throw new RuntimeException(e);
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}
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}).toList();
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var result = summarizeTrackers(trackers);
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System.out.println(result);
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//noinspection ConstantValue
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if (start!=null) System.err.println(Duration.between(start, Instant.now()));
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assert Files.readAllLines(Path.of("expected_result.txt")).getFirst().equals(result);
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}
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record FileSegment(long start, long end) {
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public long size() { return end() - start(); }
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public static List<FileSegment> forFile(Path file, int desiredSegmentsCount) throws IOException {
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try (var raf = new RandomAccessFile(file.toFile(), "r")) {
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List<FileSegment> segments = new ArrayList<>();
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long fileSize = raf.length();
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long segmentSize = fileSize / desiredSegmentsCount;
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for (int segmentIdx = 0; segmentIdx < desiredSegmentsCount; segmentIdx++) {
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long segStart = segmentIdx * segmentSize;
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long segEnd = (segmentIdx == desiredSegmentsCount - 1) ? fileSize : segStart + segmentSize;
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segStart = findSegmentBoundary(raf, segmentIdx, 0, segStart, segEnd);
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segEnd = findSegmentBoundary(raf, segmentIdx, desiredSegmentsCount - 1, segEnd, fileSize);
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segments.add(new FileSegment(segStart, segEnd));
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}
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return segments;
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}
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}
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private static long findSegmentBoundary(RandomAccessFile raf, int i, int skipForSegment, long location, long fileSize) throws IOException {
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if (i == skipForSegment) return location;
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raf.seek(location);
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while (location < fileSize) {
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location++;
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if (raf.read() == '\n') break;
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}
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return location;
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}
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}
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private static String summarizeTrackers(List<Tracker> trackers) {
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var result = new TreeMap<String, String>();
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for (int i = 0; i < HASH_NO_CLASH_MODULUS; i++) {
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String name = null;
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int min = Integer.MAX_VALUE;
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int max = Integer.MIN_VALUE;
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long sum = 0;
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long count = 0;
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for (Tracker tracker : trackers) {
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if (tracker.names[i]==null) continue;
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if (name==null) name = tracker.names[i];
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var minn = tracker.minMaxCount[i*3];
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var maxx = tracker.minMaxCount[i*3+1];
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if (minn<min) min = minn;
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if (maxx>max) max = maxx;
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count += tracker.minMaxCount[i*3+2];
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sum += tracker.sums[i];
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}
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if (name==null) continue;
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var mean = Math.round((double) sum / count) / 10.0;
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result.put(name, (min/10.0) + "/" + mean + "/" + (max/10.0));
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}
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return result.toString();
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}
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static class Tracker {
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private final int[] minMaxCount = new int[HASH_NO_CLASH_MODULUS * 3];
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private final long[] sums = new long[HASH_NO_CLASH_MODULUS];
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private final String[] names = new String[HASH_NO_CLASH_MODULUS];
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private final byte[] nameThreadLocal = new byte[64];
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private void processSegment(MappedByteBuffer segmentBuffer, long segmentEnd) {
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int startLine;
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int limit = segmentBuffer.limit();
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while ((startLine = segmentBuffer.position()) < limit) {
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int pos = startLine;
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byte b;
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int nameLength = 0, nameHash = 0;
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while (pos != segmentEnd && (b = segmentBuffer.get(pos++)) != ';') {
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nameHash = nameHash*31 + b;
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nameLength++;
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}
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int temperature = 0, sign = 1;
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outer:
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while (pos != segmentEnd && (b = segmentBuffer.get(pos++)) != '\n') {
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switch (b) {
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case '\r' :
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pos++;
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break outer;
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case '.' :
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break;
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case '-' :
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sign = -1;
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break;
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default :
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var digit = b - '0';
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assert digit >= 0 && digit <= 9;
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temperature = 10 * temperature + digit;
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}
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}
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processLine(nameHash, segmentBuffer, startLine, nameLength, temperature * sign);
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segmentBuffer.position(pos);
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}
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}
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public void processLine(int nameHash, MappedByteBuffer buffer, int nameOffset, int nameLength, int temperature) {
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var i = Math.abs(nameHash) % HASH_NO_CLASH_MODULUS;
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if (names[i]==null) {
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names[i] = parseName(buffer, nameOffset, nameLength);
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} else {
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assert parseName(buffer, nameOffset, nameLength).equals(names[i]) : parseName(buffer, nameOffset, nameLength) + "!=" + names[i];
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}
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sums[i] += temperature;
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int mmcIndex = i * 3;
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var min = minMaxCount[mmcIndex + OFFSET_MIN];
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var max = minMaxCount[mmcIndex + OFFSET_MAX];
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if (temperature < min) minMaxCount[mmcIndex + OFFSET_MIN] = temperature;
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if (temperature > max) minMaxCount[mmcIndex + OFFSET_MAX] = temperature;
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minMaxCount[mmcIndex + OFFSET_COUNT]++;
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}
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private String parseName(MappedByteBuffer buffer, int nameOffset, int nameLength) {
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buffer.get(nameOffset, nameThreadLocal, 0, nameLength);
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return new String(nameThreadLocal, 0, nameLength, StandardCharsets.UTF_8);
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}
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}
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}
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