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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.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.lang.foreign.ValueLayout.OfByte;
import java.lang.foreign.ValueLayout.OfChar;
import java.nio.channels.FileChannel;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.TreeMap;
import java.util.stream.Collectors;
public class CalculateAverage_jotschi {
private static final String FILE = "./measurements.txt";
public static void main(String[] args) throws IOException {
var filename = args.length == 0 ? FILE : args[0];
parseFile(filename);
}
@SuppressWarnings("preview")
private static void parseFile(String filename) throws IOException {
var file = new File(filename);
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r");
FileChannel fileChannel = randomAccessFile.getChannel();
MemorySegment memSeg = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileChannel.size(), Arena.global());
var results = getFileSegments(memSeg).stream().map(segment -> {
var resultMap = new ByteArrayToResultMap2();
long segmentEnd = segment.end();
MemorySegment slice = memSeg.asSlice(segment.start(), segmentEnd - segment.start());
// Up to 100 characters for a city name
var buffer = new byte[100];
int startLine;
int pos = 0;
long limit = slice.byteSize();
while ((startLine = pos) < limit) {
int currentPosition = startLine;
byte b;
int offset = 0;
int hash = 0;
while (currentPosition != segmentEnd && (b = slice.get(OfByte.JAVA_BYTE, currentPosition++)) != ';') {
buffer[offset++] = b;
hash = 31 * hash + b;
}
int temp;
int negative = 1;
// Inspired by @yemreinci to unroll this even further
if (slice.get(OfByte.JAVA_BYTE, currentPosition) == '-') {
negative = -1;
currentPosition++;
}
if (slice.get(OfByte.JAVA_BYTE, currentPosition + 1) == '.') {
temp = negative * ((slice.get(OfByte.JAVA_BYTE, currentPosition) - '0') * 10 + (slice.get(OfByte.JAVA_BYTE, currentPosition + 2) - '0'));
currentPosition += 3;
}
else {
temp = negative
* ((slice.get(OfByte.JAVA_BYTE, currentPosition) - '0') * 100
+ ((slice.get(OfByte.JAVA_BYTE, currentPosition + 1) - '0') * 10 + (slice.get(OfByte.JAVA_BYTE, currentPosition + 3) - '0')));
currentPosition += 4;
}
if (slice.get(OfByte.JAVA_BYTE, currentPosition) == '\r') {
currentPosition++;
}
currentPosition++;
resultMap.putOrMerge(buffer, 0, offset, temp / 10.0, hash);
pos = currentPosition;
}
return resultMap;
}).parallel().flatMap(partition -> partition.getAll().stream())
.collect(Collectors.toMap(e -> new String(e.key()), Entry2::value, CalculateAverage_jotschi::merge, TreeMap::new));
System.out.println(results);
}
private static List<FileSegment2> getFileSegments(MemorySegment memSeg) throws IOException {
int numberOfSegments = Runtime.getRuntime().availableProcessors();
long fileSize = memSeg.byteSize();
long segmentSize = fileSize / numberOfSegments;
List<FileSegment2> segments = new ArrayList<>(numberOfSegments);
// Pointless to split small files
if (segmentSize < 1_000_000) {
segments.add(new FileSegment2(0, fileSize));
return segments;
}
// Split the file up into even segments that match up with the CPU core count
// so that each core can process a segment of the file.
// The findSegment call ensures that the segment terminates with a newline.
for (int i = 0; i < numberOfSegments; i++) {
long segStart = i * segmentSize;
long segEnd = (i == numberOfSegments - 1) ? fileSize : segStart + segmentSize;
segStart = findSegment(i, 0, memSeg, segStart, segEnd);
segEnd = findSegment(i, numberOfSegments - 1, memSeg, segEnd, fileSize);
segments.add(new FileSegment2(segStart, segEnd));
}
return segments;
}
private static Result2 merge(Result2 v, Result2 value) {
return merge(v, value.min, value.max, value.sum, value.count);
}
private static Result2 merge(Result2 v, double value, double value1, double value2, long value3) {
v.min = Math.min(v.min, value);
v.max = Math.max(v.max, value1);
v.sum += value2;
v.count += value3;
return v;
}
private static long findSegment(int i, int skipSegment, MemorySegment memSeg, long location, long fileSize) throws IOException {
if (i != skipSegment) {
long remaining = fileSize - location;
int bufferSize = remaining < 64 ? (int) remaining : 64;
MemorySegment slice = memSeg.asSlice(location, bufferSize);
for (int offset = 0; offset < slice.byteSize(); offset++) {
if (slice.get(OfChar.JAVA_BYTE, offset) == '\n') {
return location + offset + 1;
}
}
}
return location;
}
}
class Result2 {
double min, max, sum;
long count;
Result2(double value) {
min = max = sum = value;
this.count = 1;
}
@Override
public String toString() {
return round(min) + "/" + round(sum / count) + "/" + round(max);
}
double round(double v) {
return Math.round(v * 10.0) / 10.0;
}
}
record Pair2(int slot, Result2 slotValue) {
}
record Entry2(byte[] key, Result2 value) {
}
record FileSegment2(long start, long end) {
}
class ByteArrayToResultMap2 {
public static final int MAPSIZE = 1024 * 128;
Result2[] slots = new Result2[MAPSIZE];
byte[][] keys = new byte[MAPSIZE][];
public void putOrMerge(byte[] key, int offset, int size, double temp, int hash) {
int slot = hash & (slots.length - 1);
var slotValue = slots[slot];
// Linear probe for open slot
while (slotValue != null && (keys[slot].length != size || !Arrays.equals(keys[slot], 0, size, key, offset, size))) {
slot = (slot + 1) & (slots.length - 1);
slotValue = slots[slot];
}
Result2 value = slotValue;
if (value == null) {
slots[slot] = new Result2(temp);
byte[] bytes = new byte[size];
System.arraycopy(key, offset, bytes, 0, size);
keys[slot] = bytes;
} else {
value.min = Math.min(value.min, temp);
value.max = Math.max(value.max, temp);
value.sum += temp;
value.count += 1;
}
}
// Get all pairs
public List<Entry2> getAll() {
List<Entry2> result = new ArrayList<>(slots.length);
for (int i = 0; i < slots.length; i++) {
Result2 slotValue = slots[i];
if (slotValue != null) {
result.add(new Entry2(keys[i], slotValue));
}
}
return result;
}
}
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