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