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Second submission by flippingbits - 50% performance improvement

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* feat(flippingbits): Improve parsing of measurement and few cleanups

* feat(flippingbits): Reduce chunk size to 10MB

* feat(flippingbits): Improve parsing of station names

* chore(flippingbits): Remove obsolete import

* chore(flippingbits): Few cleanups
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Stefan Sprenger 2024-01-10 20:36:22 +01:00 committed by GitHub
parent 97b1f014ad
commit a8a3876416
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 93 additions and 95 deletions
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140
src/main/java/dev/morling/onebrc/CalculateAverage_flippingbits.java
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@ -20,6 +20,7 @@ import jdk.incubator.vector.VectorOperators;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.charset.StandardCharsets;
import java.util.*;
/**
@ -33,19 +34,17 @@ public class CalculateAverage_flippingbits {
private static final String FILE = "./measurements.txt";
private static final long CHUNK_SIZE = 100 * 1024 * 1024; // 100 MB
private static final long CHUNK_SIZE = 10 * 1024 * 1024; // 10 MB
private static final int SIMD_LANE_LENGTH = ShortVector.SPECIES_MAX.length();
private static final int MAX_STATION_NAME_LENGTH = 100;
public static void main(String[] args) throws IOException {
try (var file = new RandomAccessFile(FILE, "r")) {
// Calculate chunk boundaries
long[][] chunkBoundaries = getChunkBoundaries(file);
// Process chunks
var result = Arrays.asList(chunkBoundaries).stream()
.map(chunk -> {
var result = Arrays.asList(getSegments()).stream()
.map(segment -> {
try {
return processChunk(chunk[0], chunk[1]);
return processSegment(segment[0], segment[1]);
}
catch (IOException e) {
throw new RuntimeException(e);
@ -64,73 +63,90 @@ public class CalculateAverage_flippingbits {
}
return firstMap;
})
.map(hashMap -> new TreeMap(hashMap)).get();
.map(TreeMap::new).get();
System.out.println(result);
}
}
private static long[][] getChunkBoundaries(RandomAccessFile file) throws IOException {
private static long[][] getSegments() throws IOException {
try (var file = new RandomAccessFile(FILE, "r")) {
var fileSize = file.length();
// Split file into chunks, so we can work around the size limitation of channels
var chunks = (int) (fileSize / CHUNK_SIZE);
// Split file into segments, so we can work around the size limitation of channels
var numSegments = (int) (fileSize / CHUNK_SIZE);
long[][] chunkBoundaries = new long[chunks + 1][2];
var boundaries = new long[numSegments + 1][2];
var endPointer = 0L;
for (var i = 0; i <= chunks; i++) {
// Start of chunk
chunkBoundaries[i][0] = Math.min(Math.max(endPointer, i * CHUNK_SIZE), fileSize);
for (var i = 0; i < numSegments; i++) {
// Start of segment
boundaries[i][0] = Math.min(Math.max(endPointer, i * CHUNK_SIZE), fileSize);
// Seek end of chunk, limited by the end of the file
file.seek(Math.min(chunkBoundaries[i][0] + CHUNK_SIZE - 1, fileSize));
// Seek end of segment, limited by the end of the file
file.seek(Math.min(boundaries[i][0] + CHUNK_SIZE - 1, fileSize));
// Extend chunk until end of line or file
while (true) {
var character = file.read();
if (character == '\n' || character == -1) {
break;
}
// Extend segment until end of line or file
while (file.read() != '\n') {
}
// End of chunk
// End of segment
endPointer = file.getFilePointer();
chunkBoundaries[i][1] = endPointer;
boundaries[i][1] = endPointer;
}
return chunkBoundaries;
boundaries[numSegments][0] = Math.max(endPointer, numSegments * CHUNK_SIZE);
boundaries[numSegments][1] = fileSize;
return boundaries;
}
}
private static Map<String, PartitionAggregate> processChunk(long startOfChunk, long endOfChunk)
private static Map<String, PartitionAggregate> processSegment(long startOfSegment, long endOfSegment)
throws IOException {
Map<String, PartitionAggregate> stationAggregates = new HashMap<>(10_000);
byte[] byteChunk = new byte[(int) (endOfChunk - startOfChunk)];
Map<String, PartitionAggregate> stationAggregates = new HashMap<>(50_000);
var byteChunk = new byte[(int) (endOfSegment - startOfSegment)];
var stationBuffer = new byte[MAX_STATION_NAME_LENGTH];
try (var file = new RandomAccessFile(FILE, "r")) {
file.seek(startOfChunk);
file.seek(startOfSegment);
file.read(byteChunk);
var i = 0;
while (i < byteChunk.length) {
final var startPosStation = i;
// read station name
// Station name has at least one byte
stationBuffer[0] = byteChunk[i];
i++;
// Read station name
var j = 1;
while (byteChunk[i] != ';') {
stationBuffer[j] = byteChunk[i];
j++;
i++;
}
var station = new String(Arrays.copyOfRange(byteChunk, startPosStation, i));
var station = new String(stationBuffer, 0, j, StandardCharsets.UTF_8);
i++;
// read measurement
final var startPosMeasurement = i;
while (byteChunk[i] != '\n') {
// Read measurement
var isNegative = byteChunk[i] == '-';
var measurement = 0;
if (isNegative) {
i++;
while (byteChunk[i] != '.') {
measurement = measurement * 10 + byteChunk[i] - '0';
i++;
}
var measurement = Arrays.copyOfRange(byteChunk, startPosMeasurement, i);
var aggregate = stationAggregates.getOrDefault(station, new PartitionAggregate());
aggregate.addMeasurementAndComputeAggregate(measurement);
stationAggregates.put(station, aggregate);
measurement = (measurement * 10 + byteChunk[i + 1] - '0') * -1;
}
else {
while (byteChunk[i] != '.') {
measurement = measurement * 10 + byteChunk[i] - '0';
i++;
}
measurement = measurement * 10 + byteChunk[i + 1] - '0';
}
// Update aggregate
var aggregate = stationAggregates.computeIfAbsent(station, x -> new PartitionAggregate());
aggregate.addMeasurementAndComputeAggregate((short) measurement);
i += 3;
}
stationAggregates.values().forEach(PartitionAggregate::aggregateRemainingMeasurements);
}
@ -138,40 +154,22 @@ public class CalculateAverage_flippingbits {
}
private static class PartitionAggregate {
final short[] lane = new short[SIMD_LANE_LENGTH * 2];
final short[] doubleLane = new short[SIMD_LANE_LENGTH * 2];
// Assume that we do not have more than Integer.MAX_VALUE measurements for the same station per partition
int count = 0;
long sum = 0;
short min = Short.MAX_VALUE;
short max = Short.MIN_VALUE;
public void addMeasurementAndComputeAggregate(byte[] measurementBytes) {
// Parse measurement and exploit that we know the format of the floating-point values
var measurement = measurementBytes[measurementBytes.length - 1] - '0';
var digits = 1;
for (var i = measurementBytes.length - 3; i > 0; i--) {
var num = measurementBytes[i] - '0';
measurement = measurement + (num * (int) Math.pow(10, digits));
digits++;
}
// Check if measurement is negative
if (measurementBytes[0] == '-') {
measurement = measurement * -1;
}
else {
var num = measurementBytes[0] - '0';
measurement = measurement + (num * (int) Math.pow(10, digits));
}
public void addMeasurementAndComputeAggregate(short measurement) {
// Add measurement to buffer, which is later processed by SIMD instructions
lane[count % lane.length] = (short) measurement;
doubleLane[count % doubleLane.length] = measurement;
count++;
// Once lane is full, use SIMD instructions to calculate aggregates
if (count % lane.length == 0) {
var firstVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, lane, 0);
var secondVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, lane, SIMD_LANE_LENGTH);
if (count % doubleLane.length == 0) {
var firstVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, doubleLane, 0);
var secondVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, doubleLane, SIMD_LANE_LENGTH);
var simdMin = firstVector.min(secondVector).reduceLanes(VectorOperators.MIN);
min = (short) Math.min(min, simdMin);
@ -184,8 +182,8 @@ public class CalculateAverage_flippingbits {
}
public void aggregateRemainingMeasurements() {
for (var i = 0; i < count % lane.length; i++) {
var measurement = lane[i];
for (var i = 0; i < count % doubleLane.length; i++) {
var measurement = doubleLane[i];
min = (short) Math.min(min, measurement);
max = (short) Math.max(max, measurement);
sum += measurement;
@ -204,7 +202,7 @@ public class CalculateAverage_flippingbits {
Locale.US,
"%.1f/%.1f/%.1f",
(min / 10.0),
(sum / 10.0) / count,
((sum / 10.0) / count),
(max / 10.0));
}
}