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-rw-r--r--src/main/java/dev/morling/onebrc/CalculateAverage_royvanrijn.java378
1 files changed, 164 insertions, 214 deletions
diff --git a/src/main/java/dev/morling/onebrc/CalculateAverage_royvanrijn.java b/src/main/java/dev/morling/onebrc/CalculateAverage_royvanrijn.java
index cd4d572..c74415e 100644
--- a/src/main/java/dev/morling/onebrc/CalculateAverage_royvanrijn.java
+++ b/src/main/java/dev/morling/onebrc/CalculateAverage_royvanrijn.java
@@ -28,8 +28,10 @@ import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
+import java.util.Objects;
import java.util.TreeMap;
import java.util.stream.Collectors;
+import java.util.stream.Stream;
/**
* Changelog:
@@ -47,6 +49,7 @@ import java.util.stream.Collectors;
* Segmenting files: 3150 ms (based on spullara's code)
* Not using SWAR for EOL: 2850 ms
* Inlining hash calculation: 2450 ms
+ * Replacing branchless code: 2200 ms (sometimes we need to kill the things we love)
*
* Best performing JVM on MacBook M2 Pro: 21.0.1-graal
* `sdk use java 21.0.1-graal`
@@ -55,8 +58,8 @@ import java.util.stream.Collectors;
public class CalculateAverage_royvanrijn {
private static final String FILE = "./measurements.txt";
+ // private static final String FILE = "./src/test/resources/samples/measurements-10000-unique-keys.txt";
- // mutable state now instead of records, ugh, less instantiation.
static final class Measurement {
int min, max, count;
long sum;
@@ -96,29 +99,6 @@ public class CalculateAverage_royvanrijn {
// new CalculateAverage_royvanrijn().runTests();
}
- private void testInput(final String inputString, final int start, final boolean bigEndian, final int[] expectedDelimiterAndHash, final long[] expectedCityNameLong) {
-
- byte[] input = inputString.getBytes(StandardCharsets.UTF_8);
-
- ByteBuffer buffer = ByteBuffer.wrap(input).order(bigEndian ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN);
-
- int[] output = new int[2];
- long[] cityName = new long[128];
- findNextDelimiterAndCalculateHash(buffer, SEPARATOR_PATTERN, start, buffer.limit(), output, cityName, bigEndian);
-
- if (!Arrays.equals(output, expectedDelimiterAndHash)) {
- System.out.println("Error in delimiter or hash");
- System.out.println("Expected: " + Arrays.toString(expectedDelimiterAndHash));
- System.out.println("Received: " + Arrays.toString(output));
- }
- int amountLong = 1 + ((output[0] - start) >>> 3);
- if (!Arrays.equals(cityName, 0, amountLong, expectedCityNameLong, 0, amountLong)) {
- System.out.println("Error in long array");
- System.out.println("Expected: " + Arrays.toString(expectedCityNameLong));
- System.out.println("Received: " + Arrays.toString(cityName));
- }
- }
-
private void run() throws Exception {
var results = getFileSegments(new File(FILE)).stream().map(segment -> {
@@ -128,8 +108,7 @@ public class CalculateAverage_royvanrijn {
var bb = fileChannel.map(FileChannel.MapMode.READ_ONLY, segment.start(), segmentEnd - segment.start());
// Work with any UTF-8 city name, up to 100 in length:
- var buffer = new byte[106]; // 100 + ; + -XX.X + \n
- var cityNameAsLongArray = new long[13]; // 13*8=104=kenough.
+ var cityNameAsLongArray = new long[16];
var delimiterPointerAndHash = new int[2];
// Calculate using native ordering (fastest?):
@@ -143,39 +122,39 @@ public class CalculateAverage_royvanrijn {
int limit = bb.limit();
while ((startPointer = bb.position()) < limit) {
+ int delimiterPointer, endPointer;
+
// SWAR method to find delimiter *and* record the cityname as long[] *and* calculate a hash:
findNextDelimiterAndCalculateHash(bb, SEPARATOR_PATTERN, startPointer, limit, delimiterPointerAndHash, cityNameAsLongArray, bufferIsBigEndian);
- int delimiterPointer = delimiterPointerAndHash[0];
+ delimiterPointer = delimiterPointerAndHash[0];
// Simple lookup is faster for '\n' (just three options)
- int endPointer;
-
if (delimiterPointer >= limit) {
- bb.position(limit); // skip to next line.
return measurements;
}
+ // Extract the measurement value (10x):
+ final int cityNameLength = delimiterPointer - startPointer;
- if (bb.get(delimiterPointer + 4) == '\n') {
- endPointer = delimiterPointer + 4;
+ int measuredValue;
+ int neg = 1;
+ if (bb.get(++delimiterPointer) == '-') {
+ neg = -1;
+ delimiterPointer++;
}
- else if (bb.get(delimiterPointer + 5) == '\n') {
- endPointer = delimiterPointer + 5;
+ byte dot;
+ if ((dot = (bb.get(delimiterPointer + 1))) == '.') {
+ measuredValue = neg * ((bb.get(delimiterPointer)) * 10 + (bb.get(delimiterPointer + 2)) - 528);
+ endPointer = delimiterPointer + 3;
}
else {
- endPointer = delimiterPointer + 6;
+ measuredValue = neg * (bb.get(delimiterPointer) * 100 + dot * 10 + bb.get(delimiterPointer + 3) - 5328);
+ endPointer = delimiterPointer + 4;
}
- // Read the entry in a single get():
- bb.get(buffer, 0, endPointer - startPointer);
- bb.position(endPointer + 1); // skip to next line.
-
- // Extract the measurement value (10x):
- final int cityNameLength = delimiterPointer - startPointer;
- final int measuredValueLength = endPointer - delimiterPointer - 1;
- final int measuredValue = branchlessParseInt(buffer, cityNameLength + 1, measuredValueLength);
-
// Store everything in a custom hashtable:
- measurements.update(buffer, cityNameLength, delimiterPointerAndHash[1], cityNameAsLongArray).updateWith(measuredValue);
+ measurements.update(cityNameAsLongArray, bb, cityNameLength, delimiterPointerAndHash[1]).updateWith(measuredValue);
+
+ bb.position(endPointer + 1); // skip to next line.
}
return measurements;
}
@@ -183,61 +162,18 @@ public class CalculateAverage_royvanrijn {
throw new RuntimeException(e);
}
}).parallel()
- .flatMap(v -> v.values.stream())
+ .flatMap(v -> v.get())
.collect(Collectors.toMap(e -> e.cityName, MeasurementRepository.Entry::measurement, Measurement::updateWith, TreeMap::new));
System.out.println(results);
+
+ // System.out.println("Processed: " + results.entrySet().stream().mapToLong(e -> e.getValue().count).sum());
}
/**
* -------- This section contains SWAR code (SIMD Within A Register) which processes a bytebuffer as longs to find values:
*/
private static final long SEPARATOR_PATTERN = compilePattern((byte) ';');
- private static final long[] PARTIAL_INDEX_MASKS = new long[]{ 0L, 255L, 65535L, 16777215L, 4294967295L, 1099511627775L, 281474976710655L, 72057594037927935L };
-
- public void runTests() {
-
- // Method used for debugging purposes, easy to make mistakes with all the bit hacking.
-
- // These all have the same hashes:
- testInput("Delft;-12.4", 0, true, new int[]{ 5, 1718384401 }, new long[]{ 499934586180L });
- testInput("aDelft;-12.4", 1, true, new int[]{ 6, 1718384401 }, new long[]{ 499934586180L });
-
- testInput("Delft;-12.4", 0, false, new int[]{ 5, 1718384401 }, new long[]{ 499934586180L });
- testInput("aDelft;-12.4", 1, false, new int[]{ 6, 1718384401 }, new long[]{ 499934586180L });
-
- testInput("Rotterdam;-12.4", 0, true, new int[]{ 9, -784321989 }, new long[]{ 7017859899421126482L, 109L });
- testInput("abcdefghijklmnpoqrstuvwxyzRotterdam;-12.4", 26, true, new int[]{ 35, -784321989 }, new long[]{ 7017859899421126482L, 109L });
- testInput("abcdefghijklmnpoqrstuvwxyzARotterdam;-12.4", 27, true, new int[]{ 36, -784321989 }, new long[]{ 7017859899421126482L, 109L });
-
- testInput("Rotterdam;-12.4", 0, false, new int[]{ 9, -784321989 }, new long[]{ 7017859899421126482L, 109L });
- testInput("abcdefghijklmnpoqrstuvwxyzRotterdam;-12.4", 26, false, new int[]{ 35, -784321989 }, new long[]{ 7017859899421126482L, 109L });
- testInput("abcdefghijklmnpoqrstuvwxyzARotterdam;-12.4", 27, false, new int[]{ 36, -784321989 }, new long[]{ 7017859899421126482L, 109L });
-
- // These have different hashes from the strings above:
- testInput("abcdefghijklmnpoqrstuvwxyzAROtterdam;-12.4", 27, true, new int[]{ 36, -792194501 }, new long[]{ 7017859899421118290L, 109L });
- testInput("abcdefghijklmnpoqrstuvwxyzAROtterdam;-12.4", 27, false, new int[]{ 36, -792194501 }, new long[]{ 7017859899421118290L, 109L });
-
- MeasurementRepository repository = new MeasurementRepository();
-
- // Simulate adding two entries with the same hash:
- byte[] b1 = "City1;10.0".getBytes();
- byte[] b2 = "City2;41.1".getBytes();
- repository.update(b1, 5, 1234, new long[]{ 1234L });
- repository.update(b2, 5, 1234, new long[]{ 4321L });
- // And update the same record shouldn't add a third (this happened):
- repository.update(b1, 5, 1234, new long[]{ 1234L });
-
- if (repository.values.size() != 2) {
- System.out.println("Error, should have two entries:");
- System.out.println(repository.values);
- }
-
- MeasurementRepository.Entry firstInserted = repository.values.getFirst();
- if (!firstInserted.cityName.equals("City1")) {
- System.out.println("Error, should have correct name: " + firstInserted.cityName);
- }
- }
/**
* Already looping the longs here, lets shoehorn in making a hash
@@ -249,35 +185,43 @@ public class CalculateAverage_royvanrijn {
int lCnt = 0;
for (i = start; i <= limit - 8; i += 8) {
long word = bb.getLong(i);
- if (bufferBigEndian)
+ if (bufferBigEndian) {
word = Long.reverseBytes(word); // Reversing the bytes is the cheapest way to do this
- int index = firstAnyPattern(word, pattern);
- if (index < Long.BYTES) {
- final long partialHash = word & PARTIAL_INDEX_MASKS[index];
- asLong[lCnt] = partialHash;
- hash = 961 * hash + 31 * (int) (partialHash >>> 32) + (int) partialHash;
+ }
+ final long match = word ^ pattern;
+ long mask = ((match - 0x0101010101010101L) & ~match) & 0x8080808080808080L;
+
+ if (mask != 0) {
+ final int index = Long.numberOfTrailingZeros(mask) >> 3;
output[0] = (i + index);
- output[1] = hash;
+
+ final long partialHash = word & ((mask >> 7) - 1);
+ asLong[lCnt] = partialHash;
+ output[1] = longHashStep(hash, partialHash);
return;
}
asLong[lCnt++] = word;
- hash = 961 * hash + 31 * (int) (word >>> 32) + (int) word;
+ hash = longHashStep(hash, word);
}
- // Handle remaining bytes
+ // Handle remaining bytes near the limit of the buffer:
long partialHash = 0;
+ int len = 0;
for (; i < limit; i++) {
byte read;
if ((read = bb.get(i)) == (byte) pattern) {
asLong[lCnt] = partialHash;
- hash = 961 * hash + 31 * (int) (partialHash >>> 32) + (int) partialHash;
output[0] = i;
- output[1] = hash;
+ output[1] = longHashStep(hash, partialHash);
return;
}
- partialHash = partialHash << 8 | read;
+ partialHash = partialHash | ((long) read << (len << 3));
+ len++;
}
output[0] = limit; // delimiter not found
- output[1] = hash;
+ }
+
+ private static int longHashStep(final int hash, final long word) {
+ return 31 * hash + (int) (word ^ (word >>> 32));
}
private static long compilePattern(final byte value) {
@@ -285,18 +229,9 @@ public class CalculateAverage_royvanrijn {
((long) value << 24) | ((long) value << 16) | ((long) value << 8) | (long) value;
}
- private static int firstAnyPattern(final long word, final long pattern) {
- final long match = word ^ pattern;
- long mask = match - 0x0101010101010101L;
- mask &= ~match;
- mask &= 0x8080808080808080L;
- return Long.numberOfTrailingZeros(mask) >> 3;
- }
-
record FileSegment(long start, long end) {
}
- /** Using this way to segment the file is much prettier, from spullara */
private static List<FileSegment> getFileSegments(final File file) throws IOException {
final int numberOfSegments = Runtime.getRuntime().availableProcessors();
final long fileSize = file.length();
@@ -307,52 +242,28 @@ public class CalculateAverage_royvanrijn {
return segments;
}
try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r")) {
- for (int i = 0; i < numberOfSegments; i++) {
- long segStart = i * segmentSize;
- long segEnd = (i == numberOfSegments - 1) ? fileSize : segStart + segmentSize;
- segStart = findSegment(i, 0, randomAccessFile, segStart, segEnd);
- segEnd = findSegment(i, numberOfSegments - 1, randomAccessFile, segEnd, fileSize);
-
+ long segStart = 0;
+ long segEnd = segmentSize;
+ while (segStart < fileSize) {
+ segEnd = findSegment(randomAccessFile, segEnd, fileSize);
segments.add(new FileSegment(segStart, segEnd));
+ segStart = segEnd; // Just re-use the end and go from there.
+ segEnd = Math.min(fileSize, segEnd + segmentSize);
}
}
return segments;
}
- private static long findSegment(final int i, final int skipSegment, RandomAccessFile raf, long location, final long fileSize) throws IOException {
- if (i != skipSegment) {
- raf.seek(location);
- while (location < fileSize) {
- location++;
- if (raf.read() == '\n')
- return location;
- }
+ private static long findSegment(RandomAccessFile raf, long location, final long fileSize) throws IOException {
+ raf.seek(location);
+ while (location < fileSize) {
+ location++;
+ if (raf.read() == '\n')
+ return location;
}
return location;
}
- /**
- * Branchless parser, goes from String to int (10x):
- * "-1.2" to -12
- * "40.1" to 401
- * etc.
- *
- * @param input
- * @return int value x10
- */
- private static int branchlessParseInt(final byte[] input, final int start, final int length) {
- // 0 if positive, 1 if negative
- final int negative = ~(input[start] >> 4) & 1;
- // 0 if nr length is 3, 1 if length is 4
- final int has4 = ((length - negative) >> 2) & 1;
-
- final int digit1 = input[start + negative] - '0';
- final int digit2 = input[start + negative + has4];
- final int digit3 = input[start + negative + has4 + 2];
-
- return (-negative ^ (has4 * (digit1 * 100) + digit2 * 10 + digit3 - 528) - negative); // 528 == ('0' * 10 + '0')
- }
-
// branchless max (unprecise for large numbers, but good enough)
static int max(final int a, final int b) {
final int diff = a - b;
@@ -373,88 +284,81 @@ public class CalculateAverage_royvanrijn {
* So I've written an extremely simple linear probing hashmap that should work well enough.
*/
class MeasurementRepository {
- private int size = 16384;// 16384; // Much larger than the number of cities, needs power of two
- private int[] indices = new int[size]; // Hashtable is just an int[]
+ private int tableSize = 1 << 20; // can grow in theory, made large enough not to (this is faster)
+ private int tableMask = (tableSize - 1);
+ private int tableLimit = (int) (tableSize * LOAD_FACTOR);
+ private int tableFilled = 0;
+ private static final float LOAD_FACTOR = 0.8f;
- MeasurementRepository() {
- populateEmptyIndices(indices);
- }
+ private Entry[] table = new Entry[tableSize];
- private void populateEmptyIndices(int[] array) {
- // Optimized fill with -1, fastest method:
- int len = array.length;
- array[0] = -1;
- // Value of i will be [1, 2, 4, 8, 16, 32, ..., len]
- for (int i = 1; i < len; i += i) {
- System.arraycopy(array, 0, array, i, i);
- }
- }
-
- private final List<Entry> values = new ArrayList<>(512);
-
- record Entry(int hash, long[] cityNameAsLong, String cityName, Measurement measurement) {
+ record Entry(int hash, long[] nameBytesInLong, String cityName, Measurement measurement) {
@Override
public String toString() {
return cityName + "=" + measurement;
}
}
- public Measurement update(byte[] buffer, int length, int calculatedHash, long[] cityNameAsLongArray) {
-
- final int cityNameAsLongLength = 1 + (length >>> 3); // amount of longs that captures this cityname
+ public Measurement update(long[] nameBytesInLong, ByteBuffer bb, int length, int calculatedHash) {
- int hashtableIndex = (size - 1) & calculatedHash;
- int valueIndex;
+ final int nameBytesInLongLength = 1 + (length >>> 3);
- Entry retrievedEntry = null;
+ int index = calculatedHash & tableMask;
+ Entry tableEntry;
+ while ((tableEntry = table[index]) != null
+ && (tableEntry.hash != calculatedHash || !arrayEquals(tableEntry.nameBytesInLong, nameBytesInLong, nameBytesInLongLength))) { // search for the right spot
+ index = (index + 1) & tableMask;
+ }
- while (true) { // search for the right spot
- if ((valueIndex = indices[hashtableIndex]) == -1) {
- break; // Empty slot found, stop the loop
- }
- else {
- // Non-empty slot, retrieve entry
- if ((retrievedEntry = values.get(valueIndex)).hash == calculatedHash &&
- arrayEquals(retrievedEntry.cityNameAsLong, cityNameAsLongArray, cityNameAsLongLength)) {
- break; // Both hash and cityname match, stop the loop
- }
- }
- // Move to the next index
- hashtableIndex = (hashtableIndex + 1) % size;
+ if (tableEntry != null) {
+ return tableEntry.measurement;
}
- if (valueIndex >= 0) {
- return retrievedEntry.measurement;
+ // --- This is a brand new entry, insert into the hashtable and do the extra calculations (once!) do slower calculations here.
+ Measurement measurement = new Measurement();
+
+ // Now create a string:
+ byte[] buffer = new byte[length];
+ bb.get(buffer, 0, length);
+ String cityName = new String(buffer, 0, length);
+
+ // Store the long[] for faster equals:
+ long[] nameBytesInLongCopy = new long[nameBytesInLongLength];
+ System.arraycopy(nameBytesInLong, 0, nameBytesInLongCopy, 0, nameBytesInLongLength);
+
+ // And add entry:
+ Entry toAdd = new Entry(calculatedHash, nameBytesInLongCopy, cityName, measurement);
+ table[index] = toAdd;
+
+ // Resize the table if filled too much:
+ if (++tableFilled > tableLimit) {
+ resizeTable();
}
- // --- This is a brand new entry, insert into the hashtable and do the extra calculations (once!)
-
- // Keep the already processed longs for fast equals:
- long[] cityNameAsLongArrayCopy = new long[cityNameAsLongLength];
- System.arraycopy(cityNameAsLongArray, 0, cityNameAsLongArrayCopy, 0, cityNameAsLongLength);
-
- Entry toAdd = new Entry(calculatedHash, cityNameAsLongArrayCopy, new String(buffer, 0, length), new Measurement());
-
- // Code to regrow (if we get more unique entries): (not needed/not optimized yet)
- // if (values.size() > size / 2) {
- // // We probably don't want this...
- //
- // int newSize = size << 1;
- // int[] newIndices = new int[newSize];
- // populateEmptyIndices(newIndices);
- // for (int i = 0; i < values.size(); i++) {
- // Entry e = values.get(i);
- // int updatedIndex = (newSize - 1) & e.hash;
- // newIndices[updatedIndex] = i;
- // }
- // indices = newIndices;
- // size = newSize;
- // }
- indices[hashtableIndex] = values.size();
-
- values.add(toAdd);
return toAdd.measurement;
}
+
+ private void resizeTable() {
+ // Resize the table:
+ Entry[] oldEntries = table;
+ table = new Entry[tableSize <<= 2]; // x2
+ tableMask = (tableSize - 1);
+ tableLimit = (int) (tableSize * LOAD_FACTOR);
+
+ for (Entry entry : oldEntries) {
+ if (entry != null) {
+ int updatedTableIndex = entry.hash & tableMask;
+ while (table[updatedTableIndex] != null) {
+ updatedTableIndex = (updatedTableIndex + 1) & tableMask;
+ }
+ table[updatedTableIndex] = entry;
+ }
+ }
+ }
+
+ public Stream<Entry> get() {
+ return Arrays.stream(table).filter(Objects::nonNull);
+ }
}
/**
@@ -467,4 +371,50 @@ public class CalculateAverage_royvanrijn {
}
return true;
}
+
+ public void runTests() {
+ // Method used for debugging purposes, easy to make mistakes with all the bit hacking.
+
+ // These all have the same hashes:
+ testInput("Delft;-12.4", 0, true, new int[]{ 5, 1718384401 }, new long[]{ 499934586180L });
+ testInput("aDelft;-12.4", 1, true, new int[]{ 6, 1718384401 }, new long[]{ 499934586180L });
+
+ testInput("Delft;-12.4", 0, false, new int[]{ 5, 1718384401 }, new long[]{ 499934586180L });
+ testInput("aDelft;-12.4", 1, false, new int[]{ 6, 1718384401 }, new long[]{ 499934586180L });
+
+ testInput("Rotterdam;-12.4", 0, true, new int[]{ 9, -784321989 }, new long[]{ 7017859899421126482L, 109L });
+ testInput("abcdefghijklmnpoqrstuvwxyzRotterdam;-12.4", 26, true, new int[]{ 35, -784321989 }, new long[]{ 7017859899421126482L, 109L });
+ testInput("abcdefghijklmnpoqrstuvwxyzARotterdam;-12.4", 27, true, new int[]{ 36, -784321989 }, new long[]{ 7017859899421126482L, 109L });
+
+ testInput("Rotterdam;-12.4", 0, false, new int[]{ 9, -784321989 }, new long[]{ 7017859899421126482L, 109L });
+ testInput("abcdefghijklmnpoqrstuvwxyzRotterdam;-12.4", 26, false, new int[]{ 35, -784321989 }, new long[]{ 7017859899421126482L, 109L });
+ testInput("abcdefghijklmnpoqrstuvwxyzARotterdam;-12.4", 27, false, new int[]{ 36, -784321989 }, new long[]{ 7017859899421126482L, 109L });
+
+ // These have different hashes from the strings above:
+ testInput("abcdefghijklmnpoqrstuvwxyzAROtterdam;-12.4", 27, true, new int[]{ 36, -792194501 }, new long[]{ 7017859899421118290L, 109L });
+ testInput("abcdefghijklmnpoqrstuvwxyzAROtterdam;-12.4", 27, false, new int[]{ 36, -792194501 }, new long[]{ 7017859899421118290L, 109L });
+ }
+
+ private void testInput(final String inputString, final int start, final boolean bigEndian, final int[] expectedDelimiterAndHash, final long[] expectedCityNameLong) {
+
+ byte[] input = inputString.getBytes(StandardCharsets.UTF_8);
+
+ ByteBuffer buffer = ByteBuffer.wrap(input).order(bigEndian ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN);
+
+ int[] output = new int[2];
+ long[] cityName = new long[128];
+ findNextDelimiterAndCalculateHash(buffer, SEPARATOR_PATTERN, start, buffer.limit(), output, cityName, bigEndian);
+
+ if (!Arrays.equals(output, expectedDelimiterAndHash)) {
+ System.out.println("Error in delimiter or hash");
+ System.out.println("Expected: " + Arrays.toString(expectedDelimiterAndHash));
+ System.out.println("Received: " + Arrays.toString(output));
+ }
+ int amountLong = 1 + ((output[0] - start) >>> 3);
+ if (!Arrays.equals(cityName, 0, amountLong, expectedCityNameLong, 0, amountLong)) {
+ System.out.println("Error in long array");
+ System.out.println("Expected: " + Arrays.toString(expectedCityNameLong));
+ System.out.println("Received: " + Arrays.toString(cityName));
+ }
+ }
}
generated by cgit v1.2.3 (git 2.25.1) at 2026-05-13 10:28:24 +0000