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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.IOException;
import java.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.lang.foreign.ValueLayout;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
public class CalculateAverage_anitasv {
private static final String FILE = "./measurements.txt";
private record Shard(MemorySegment mmapMemory,
long chunkStart, long chunkEnd) {
byte getByte(long address) {
return mmapMemory.get(ValueLayout.JAVA_BYTE, address);
}
long indexOf(long position, byte ch) {
ByteBuffer buf = mmapMemory.asSlice(position,
Math.min(128, mmapMemory.byteSize() - position))
.asByteBuffer();
while (buf.hasRemaining()) {
if (buf.get() == ch) {
return position + buf.position() - 1;
}
}
return -1;
}
byte[] getRange(long start, long end) {
return mmapMemory.asSlice(start, end - start).toArray(ValueLayout.JAVA_BYTE);
}
int parseDouble(long start, long end) {
int normalized = 0;
boolean sign = true;
long index = start;
if (getByte(index) == '-') {
index++;
sign = false;
}
boolean hasDot = false;
for (; index < end; index++) {
byte ch = getByte(index);
if (ch != '.') {
normalized = normalized * 10 + (ch - '0');
} else {
hasDot = true;
}
}
if (!hasDot) {
normalized *= 10;
}
if (!sign) {
normalized = -normalized;
}
return normalized;
}
public int computeHash(long position, long stationEnd) {
ByteBuffer buf2 = mmapMemory.asSlice(position, stationEnd - position)
.asByteBuffer();
return buf2.hashCode();
}
public boolean matches(byte[] existingStation, long start, long end) {
ByteBuffer buf1 = ByteBuffer.wrap(existingStation);
ByteBuffer buf2 = mmapMemory.asSlice(start, end - start).asByteBuffer();
return buf1.equals(buf2);
}
}
private record ResultRow(byte[] station, IntSummaryStatistics statistics) {
public String toString() {
return STR."\{new String(station, StandardCharsets.UTF_8)} : \{statToString(statistics)}";
}
}
private static Map<String, IntSummaryStatistics> process(Shard shard) {
HashMap<Integer, List<ResultRow>> result = new HashMap<>(1 << 14);
boolean skip = shard.chunkStart != 0;
for (long position = shard.chunkStart; position < shard.chunkEnd; position++) {
if (skip) {
position = shard.indexOf(position, (byte) '\n');
skip = false;
}
else {
long stationEnd = shard.indexOf(position, (byte) ';');
int hash = shard.computeHash(position, stationEnd);
long temperatureEnd = shard.indexOf(stationEnd + 1, (byte) '\n');
int temperature = shard.parseDouble(stationEnd + 1, temperatureEnd);
List<ResultRow> collisions = result.get(hash);
if (collisions == null) {
collisions = new ArrayList<>();
result.put(hash, collisions);
}
boolean found = false;
for (ResultRow existing : collisions) {
byte[] existingStation = existing.station();
if (shard.matches(existingStation, position, stationEnd)) {
existing.statistics.accept(temperature);
found = true;
break;
}
}
if (!found) {
IntSummaryStatistics stats = new IntSummaryStatistics();
stats.accept(temperature);
ResultRow rr = new ResultRow(shard.getRange(position, stationEnd), stats);
collisions.add(rr);
}
position = temperatureEnd;
}
}
return result.values()
.stream()
.flatMap(Collection::stream)
.map(rr -> new AbstractMap.SimpleImmutableEntry<>(
new String(rr.station, StandardCharsets.UTF_8),
rr.statistics))
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
}
private static Map<String, IntSummaryStatistics> combineResults(List<Map<String, IntSummaryStatistics>> list) {
Map<String, IntSummaryStatistics> output = HashMap.newHashMap(1024);
for (Map<String, IntSummaryStatistics> map : list) {
for (Map.Entry<String, IntSummaryStatistics> entry : map.entrySet()) {
output.compute(entry.getKey(), (ignore, val) -> {
if (val == null) {
return entry.getValue();
}
else {
val.combine(entry.getValue());
return val;
}
});
}
}
return output;
}
private static Map<String, IntSummaryStatistics> master(MemorySegment mmapMemory) {
long totalBytes = mmapMemory.byteSize();
int numWorkers = Runtime.getRuntime().availableProcessors();
long chunkSize = Math.ceilDiv(totalBytes, numWorkers);
return combineResults(IntStream.range(0, numWorkers)
.parallel()
.mapToObj(workerId -> {
long chunkStart = workerId * chunkSize;
long chunkEnd = Math.min(chunkStart + chunkSize + 1, totalBytes);
return new Shard(mmapMemory, chunkStart, chunkEnd);
})
.map(CalculateAverage_anitasv::process)
.toList());
}
public static Map<String, IntSummaryStatistics> start() throws IOException {
try (FileChannel fileChannel = FileChannel.open(Path.of(FILE),
StandardOpenOption.READ)) {
long fileSize = fileChannel.size();
MemorySegment mmapMemory = fileChannel.map(
FileChannel.MapMode.READ_ONLY,
0, fileSize, Arena.global());
return master(mmapMemory);
}
}
private static Map<String, String> toPrintMap(Map<String, IntSummaryStatistics> output) {
Map<String, String> outputStr = new TreeMap<>();
for (Map.Entry<String, IntSummaryStatistics> entry : output.entrySet()) {
IntSummaryStatistics stat = entry.getValue();
outputStr.put(entry.getKey(), statToString(stat));
}
return outputStr;
}
private static String statToString(IntSummaryStatistics stat) {
return STR."\{stat.getMin() / 10.0}/\{Math.round(stat.getAverage()) / 10.0}/\{stat.getMax() / 10.0}";
}
public static void main(String[] args) throws IOException {
System.out.println(toPrintMap(start()));
}
}
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