Second submission by flippingbits - 50% performance improvement
* 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
This commit is contained in:
Stefan Sprenger
GitHub
parent
97b1f014ad
commit
a8a3876416
@ -20,6 +20,7 @@ import jdk.incubator.vector.VectorOperators;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.nio.charset.StandardCharsets;
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import java.util.*;
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/**
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@ -33,103 +34,118 @@ public class CalculateAverage_flippingbits {
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private static final String FILE = "./measurements.txt";
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private static final long CHUNK_SIZE = 100 * 1024 * 1024; // 100 MB
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private static final long CHUNK_SIZE = 10 * 1024 * 1024; // 10 MB
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private static final int SIMD_LANE_LENGTH = ShortVector.SPECIES_MAX.length();
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public static void main(String[] args) throws IOException {
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try (var file = new RandomAccessFile(FILE, "r")) {
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// Calculate chunk boundaries
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long[][] chunkBoundaries = getChunkBoundaries(file);
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// Process chunks
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var result = Arrays.asList(chunkBoundaries).stream()
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.map(chunk -> {
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try {
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return processChunk(chunk[0], chunk[1]);
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}
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catch (IOException e) {
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throw new RuntimeException(e);
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}
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})
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.parallel()
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.reduce((firstMap, secondMap) -> {
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for (var entry : secondMap.entrySet()) {
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PartitionAggregate firstAggregate = firstMap.get(entry.getKey());
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if (firstAggregate == null) {
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firstMap.put(entry.getKey(), entry.getValue());
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}
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else {
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firstAggregate.mergeWith(entry.getValue());
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}
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}
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return firstMap;
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})
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.map(hashMap -> new TreeMap(hashMap)).get();
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private static final int MAX_STATION_NAME_LENGTH = 100;
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System.out.println(result);
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}
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public static void main(String[] args) throws IOException {
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var result = Arrays.asList(getSegments()).stream()
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.map(segment -> {
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try {
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return processSegment(segment[0], segment[1]);
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}
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catch (IOException e) {
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throw new RuntimeException(e);
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}
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})
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.parallel()
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.reduce((firstMap, secondMap) -> {
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for (var entry : secondMap.entrySet()) {
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PartitionAggregate firstAggregate = firstMap.get(entry.getKey());
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if (firstAggregate == null) {
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firstMap.put(entry.getKey(), entry.getValue());
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}
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else {
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firstAggregate.mergeWith(entry.getValue());
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}
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}
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return firstMap;
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})
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.map(TreeMap::new).get();
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System.out.println(result);
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}
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private static long[][] getChunkBoundaries(RandomAccessFile file) throws IOException {
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var fileSize = file.length();
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// Split file into chunks, so we can work around the size limitation of channels
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var chunks = (int) (fileSize / CHUNK_SIZE);
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private static long[][] getSegments() throws IOException {
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try (var file = new RandomAccessFile(FILE, "r")) {
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var fileSize = file.length();
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// Split file into segments, so we can work around the size limitation of channels
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var numSegments = (int) (fileSize / CHUNK_SIZE);
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long[][] chunkBoundaries = new long[chunks + 1][2];
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var endPointer = 0L;
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var boundaries = new long[numSegments + 1][2];
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var endPointer = 0L;
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for (var i = 0; i <= chunks; i++) {
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// Start of chunk
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chunkBoundaries[i][0] = Math.min(Math.max(endPointer, i * CHUNK_SIZE), fileSize);
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for (var i = 0; i < numSegments; i++) {
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// Start of segment
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boundaries[i][0] = Math.min(Math.max(endPointer, i * CHUNK_SIZE), fileSize);
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// Seek end of chunk, limited by the end of the file
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file.seek(Math.min(chunkBoundaries[i][0] + CHUNK_SIZE - 1, fileSize));
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// Seek end of segment, limited by the end of the file
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file.seek(Math.min(boundaries[i][0] + CHUNK_SIZE - 1, fileSize));
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// Extend chunk until end of line or file
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while (true) {
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var character = file.read();
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if (character == '\n' || character == -1) {
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break;
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// Extend segment until end of line or file
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while (file.read() != '\n') {
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}
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// End of segment
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endPointer = file.getFilePointer();
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boundaries[i][1] = endPointer;
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}
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// End of chunk
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endPointer = file.getFilePointer();
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chunkBoundaries[i][1] = endPointer;
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}
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boundaries[numSegments][0] = Math.max(endPointer, numSegments * CHUNK_SIZE);
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boundaries[numSegments][1] = fileSize;
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return chunkBoundaries;
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return boundaries;
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}
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}
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private static Map<String, PartitionAggregate> processChunk(long startOfChunk, long endOfChunk)
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private static Map<String, PartitionAggregate> processSegment(long startOfSegment, long endOfSegment)
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throws IOException {
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Map<String, PartitionAggregate> stationAggregates = new HashMap<>(10_000);
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byte[] byteChunk = new byte[(int) (endOfChunk - startOfChunk)];
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Map<String, PartitionAggregate> stationAggregates = new HashMap<>(50_000);
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var byteChunk = new byte[(int) (endOfSegment - startOfSegment)];
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var stationBuffer = new byte[MAX_STATION_NAME_LENGTH];
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try (var file = new RandomAccessFile(FILE, "r")) {
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file.seek(startOfChunk);
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file.seek(startOfSegment);
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file.read(byteChunk);
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var i = 0;
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while (i < byteChunk.length) {
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final var startPosStation = i;
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// read station name
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// Station name has at least one byte
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stationBuffer[0] = byteChunk[i];
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i++;
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// Read station name
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var j = 1;
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while (byteChunk[i] != ';') {
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stationBuffer[j] = byteChunk[i];
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j++;
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i++;
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}
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var station = new String(Arrays.copyOfRange(byteChunk, startPosStation, i));
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var station = new String(stationBuffer, 0, j, StandardCharsets.UTF_8);
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i++;
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// read measurement
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final var startPosMeasurement = i;
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while (byteChunk[i] != '\n') {
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// Read measurement
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var isNegative = byteChunk[i] == '-';
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var measurement = 0;
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if (isNegative) {
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i++;
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while (byteChunk[i] != '.') {
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measurement = measurement * 10 + byteChunk[i] - '0';
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i++;
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}
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measurement = (measurement * 10 + byteChunk[i + 1] - '0') * -1;
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}
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else {
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while (byteChunk[i] != '.') {
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measurement = measurement * 10 + byteChunk[i] - '0';
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i++;
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}
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measurement = measurement * 10 + byteChunk[i + 1] - '0';
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}
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var measurement = Arrays.copyOfRange(byteChunk, startPosMeasurement, i);
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var aggregate = stationAggregates.getOrDefault(station, new PartitionAggregate());
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aggregate.addMeasurementAndComputeAggregate(measurement);
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stationAggregates.put(station, aggregate);
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i++;
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// Update aggregate
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var aggregate = stationAggregates.computeIfAbsent(station, x -> new PartitionAggregate());
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aggregate.addMeasurementAndComputeAggregate((short) measurement);
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i += 3;
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}
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stationAggregates.values().forEach(PartitionAggregate::aggregateRemainingMeasurements);
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}
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@ -138,40 +154,22 @@ public class CalculateAverage_flippingbits {
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}
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private static class PartitionAggregate {
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final short[] lane = new short[SIMD_LANE_LENGTH * 2];
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final short[] doubleLane = new short[SIMD_LANE_LENGTH * 2];
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// Assume that we do not have more than Integer.MAX_VALUE measurements for the same station per partition
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int count = 0;
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long sum = 0;
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short min = Short.MAX_VALUE;
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short max = Short.MIN_VALUE;
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public void addMeasurementAndComputeAggregate(byte[] measurementBytes) {
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// Parse measurement and exploit that we know the format of the floating-point values
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var measurement = measurementBytes[measurementBytes.length - 1] - '0';
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var digits = 1;
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for (var i = measurementBytes.length - 3; i > 0; i--) {
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var num = measurementBytes[i] - '0';
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measurement = measurement + (num * (int) Math.pow(10, digits));
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digits++;
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}
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// Check if measurement is negative
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if (measurementBytes[0] == '-') {
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measurement = measurement * -1;
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}
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else {
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var num = measurementBytes[0] - '0';
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measurement = measurement + (num * (int) Math.pow(10, digits));
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}
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public void addMeasurementAndComputeAggregate(short measurement) {
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// Add measurement to buffer, which is later processed by SIMD instructions
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lane[count % lane.length] = (short) measurement;
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doubleLane[count % doubleLane.length] = measurement;
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count++;
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// Once lane is full, use SIMD instructions to calculate aggregates
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if (count % lane.length == 0) {
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var firstVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, lane, 0);
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var secondVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, lane, SIMD_LANE_LENGTH);
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if (count % doubleLane.length == 0) {
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var firstVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, doubleLane, 0);
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var secondVector = ShortVector.fromArray(ShortVector.SPECIES_MAX, doubleLane, SIMD_LANE_LENGTH);
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var simdMin = firstVector.min(secondVector).reduceLanes(VectorOperators.MIN);
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min = (short) Math.min(min, simdMin);
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@ -184,8 +182,8 @@ public class CalculateAverage_flippingbits {
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}
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public void aggregateRemainingMeasurements() {
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for (var i = 0; i < count % lane.length; i++) {
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var measurement = lane[i];
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for (var i = 0; i < count % doubleLane.length; i++) {
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var measurement = doubleLane[i];
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min = (short) Math.min(min, measurement);
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max = (short) Math.max(max, measurement);
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sum += measurement;
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@ -204,7 +202,7 @@ public class CalculateAverage_flippingbits {
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Locale.US,
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"%.1f/%.1f/%.1f",
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(min / 10.0),
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(sum / 10.0) / count,
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((sum / 10.0) / count),
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(max / 10.0));
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}
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}
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