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Locally another 5% faster, much faster for larger set, made more general (#352)

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Roy van Rijn 2024-01-12 21:00:12 +01:00 committed by GitHub
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1 changed files with 115 additions and 77 deletions
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src/main/java/dev/morling/onebrc/CalculateAverage_royvanrijn.java
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@ -23,7 +23,6 @@ import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
@ -53,8 +52,13 @@ import sun.misc.Unsafe;
* Various tweaks for Linux/cache 1550 ms (should/could make a difference on target machine)
* Improved layout/predictability: 1400 ms
* Delayed String creation again: 1350 ms
* Remove writing to buffer: 1335 ms
* Optimized collecting at the end: 1310 ms
* Adding a lot of comments: priceless
*
* Big thanks to Francesco Nigro, Thomas Wuerthinger, Quan Anh Mai for ideas.
*
* Follow me at: @royvanrijn
*/
public class CalculateAverage_royvanrijn {
@ -74,29 +78,24 @@ public class CalculateAverage_royvanrijn {
}
public static void main(String[] args) throws Exception {
// Calculate input segments.
final int numberOfChunks = Runtime.getRuntime().availableProcessors();
final long[] chunks = getSegments(numberOfChunks);
final List<Entry[]> repositories = IntStream.range(0, chunks.length - 1)
final Map<String, Entry> measurements = HashMap.newHashMap(1 << 10);
IntStream.range(0, chunks.length - 1)
.mapToObj(chunkIndex -> processMemoryArea(chunks[chunkIndex], chunks[chunkIndex + 1]))
.parallel()
.toList();
// Sometimes simple is better:
final HashMap<String, Entry> measurements = HashMap.newHashMap(1 << 10);
for (Entry[] entries : repositories) {
for (Entry entry : entries) {
if (entry != null)
measurements.merge(extractedCityFromLongArray(entry.data, entry.length), entry, Entry::mergeWith);
}
}
.forEachOrdered(repo -> { // make sure it's ordered, no concurrent map
for (Entry entry : repo) {
if (entry != null)
measurements.merge(turnLongArrayIntoString(entry.data, entry.length), entry, Entry::mergeWith);
}
});
System.out.print("{" +
measurements.entrySet().stream().sorted(Map.Entry.comparingByKey()).map(Object::toString).collect(Collectors.joining(", ")));
System.out.println("}");
}
/**
@ -123,15 +122,20 @@ public class CalculateAverage_royvanrijn {
}
}
private static final int TABLE_SIZE = 1 << 19; // large enough for the contest.
private static final int TABLE_MASK = (TABLE_SIZE - 1);
// This is where I store the hashtable entry data in the "hot loop"
// The long[] contains the name in bytes (yeah, confusing)
// I've tried flyweight-ing, carrying all the data in a single byte[],
// where you offset type-indices: min:int,max:int,count:int,etc.
//
// The performance was just a little worse than this simple class.
static final class Entry {
private final long[] data;
private int min, max, count, length;
private long sum;
Entry(final long[] data, int length, int temp) {
private int min, max, count;
private byte length;
private long sum;
private final long[] data;
Entry(final long[] data, byte length, int temp) {
this.data = data;
this.length = length;
this.min = temp;
@ -164,127 +168,161 @@ public class CalculateAverage_royvanrijn {
}
}
/**
* Delay String creation until the end:
* @param data
* @param length
* @return
*/
private static String extractedCityFromLongArray(final long[] data, final int length) {
// Initiate as late as possible:
// Only parse the String at the final end, when we have only the needed entries left that we need to output:
private static String turnLongArrayIntoString(final long[] data, final int length) {
// Create our target byte[]
final byte[] bytes = new byte[length];
// The power of magic allows us to just copy the memory in there.
UNSAFE.copyMemory(data, Unsafe.ARRAY_LONG_BASE_OFFSET, bytes, Unsafe.ARRAY_BYTE_BASE_OFFSET, length);
// And construct a String()
return new String(bytes, StandardCharsets.UTF_8);
}
private static Entry createNewEntry(final long[] buffer, final int lengthLongs, final int lengthBytes, final int temp) {
private static Entry createNewEntry(final long fromAddress, final int lengthLongs, final byte lengthBytes, final int temp) {
// Make a copy of our working buffer, store this in a new Entry:
final long[] bufferCopy = new long[lengthLongs];
System.arraycopy(buffer, 0, bufferCopy, 0, lengthLongs);
// Add the entry:
// Just copy everything over, bytes into the long[]
UNSAFE.copyMemory(null, fromAddress, bufferCopy, Unsafe.ARRAY_BYTE_BASE_OFFSET, lengthBytes);
return new Entry(bufferCopy, lengthBytes, temp);
}
private static final int TABLE_SIZE = 1 << 19;
private static final int TABLE_MASK = (TABLE_SIZE - 1);
private static Entry[] processMemoryArea(final long fromAddress, final long toAddress) {
final Entry[] table = new Entry[TABLE_SIZE];
final long[] buffer = new long[16];
long ptr = fromAddress;
int bufferPtr;
int packedBytes;
long hash;
long ptr = fromAddress;
long word;
long mask;
final Entry[] table = new Entry[TABLE_SIZE];
// Go from start to finish address through the bytes:
while (ptr < toAddress) {
final long startAddress = ptr;
bufferPtr = 0;
hash = 1;
packedBytes = 1;
hash = 0;
word = UNSAFE.getLong(ptr);
mask = getDelimiterMask(word);
// Removed writing to a buffer here, why would we, we know the address and we'll need to check there anyway.
while (mask == 0) {
buffer[bufferPtr++] = word;
// If the mask is zero, we have no ';'
packedBytes++;
// So we continue building the hash:
hash ^= word;
ptr += 8;
// And getting a new value and mask:
word = UNSAFE.getLong(ptr);
mask = getDelimiterMask(word);
}
// Found delimiter:
final long delimiterAddress = ptr + (Long.numberOfTrailingZeros(mask) >> 3);
final long numberBits = UNSAFE.getLong(delimiterAddress + 1);
final int delimiterByte = Long.numberOfTrailingZeros(mask);
final long delimiterAddress = ptr + (delimiterByte >> 3);
// Finish the masks and hash:
word = word & ((mask >> 7) - 1);
buffer[bufferPtr++] = word;
hash ^= word;
final long partialWord = word & ((mask >>> 7) - 1);
hash ^= partialWord;
final long invNumberBits = ~numberBits;
final int decimalSepPos = Long.numberOfTrailingZeros(invNumberBits & DOT_BITS);
// Read a long value from memory starting from the delimiter + 1, the number part:
final long numberBytes = UNSAFE.getLong(delimiterAddress + 1);
final long invNumberBytes = ~numberBytes;
// Update counter asap, lets CPU predict.
// Adjust our pointer
final int decimalSepPos = Long.numberOfTrailingZeros(invNumberBytes & DOT_BITS);
ptr = delimiterAddress + (decimalSepPos >> 3) + 4;
// Awesome idea of merykitty:
final int temp = extractTemp(numberBits, invNumberBits, decimalSepPos);
int intHash = (int) (hash ^ (hash >>> 33)); // offset for extra entropy
// Calculate the final hash and index of the table:
int intHash = (int) (hash ^ (hash >> 32));
intHash = intHash ^ (intHash >> 17);
int index = intHash & TABLE_MASK;
// Find or insert the entry:
while (true) {
Entry tableEntry = table[index];
if (tableEntry == null) {
final int length = (int) (delimiterAddress - startAddress);
table[index] = createNewEntry(buffer, bufferPtr, length, temp);
final int temp = extractTemp(decimalSepPos, invNumberBytes, numberBytes);
// Create a new entry:
final byte length = (byte) (delimiterAddress - startAddress);
table[index] = createNewEntry(startAddress, packedBytes, length, temp);
break;
}
else if (bufferPtr == tableEntry.data.length) {
if (!arrayEquals(buffer, tableEntry.data, bufferPtr)) {
index = (index + 1) & TABLE_MASK;
continue;
}
// No differences in array
// Don't bother re-checking things here like hash or length.
// we'll need to check the content anyway if it's a hit, which is most times
else if (memoryEqualsEntry(startAddress, tableEntry.data, partialWord, packedBytes)) {
// temperature, you're not temporary my friend
final int temp = extractTemp(decimalSepPos, invNumberBytes, numberBytes);
// No differences, same entry:
tableEntry.updateWith(temp);
break;
}
// Move to the next index
// Move to the next in the table, linear probing:
index = (index + 1) & TABLE_MASK;
}
}
return table;
}
private static int extractTemp(final long numberBits, final long invNumberBits, final int decimalSepPos) {
/*
* `___` ___ ___ _ ___` ` ___ ` _ ` _ ` _` ___
* / ` \| _ \ __| \| \ \ / /_\ | | | | | | __|
* | () | _ / __|| . |\ V / _ \| |_| |_| | ._|
* \___/|_| |___|_|\_| \_/_/ \_\___|\___/|___|
* ---------------- BETTER SOFTWARE, FASTER --
*
* https://www.openvalue.eu/
*
* Made you look.
*
*/
private static final long DOT_BITS = 0x10101000;
private static final long MAGIC_MULTIPLIER = (100 * 0x1000000 + 10 * 0x10000 + 1);
private static int extractTemp(final int decimalSepPos, final long invNumberBits, final long numberBits) {
// Awesome idea of merykitty:
int min28 = (28 - decimalSepPos);
// Calculates the sign
final long signed = (invNumberBits << 59) >> 63;
final long minusFilter = ~(signed & 0xFF);
final long digits = ((numberBits & minusFilter) << (28 - decimalSepPos)) & 0x0F000F0F00L;
final long absValue = ((digits * MAGIC_MULTIPLIER) >>> 32) & 0x3FF; // filter just the result
// Use the pre-calculated decimal position to adjust the values
final long digits = ((numberBits & minusFilter) << min28) & 0x0F000F0F00L;
// Multiply by a magic (100 * 0x1000000 + 10 * 0x10000 + 1), to get the result
final long absValue = ((digits * MAGIC_MULTIPLIER) >>> 32) & 0x3FF;
// And perform abs()
final int temp = (int) ((absValue + signed) ^ signed); // non-patented method of doing the same trick
return temp;
}
private static long getDelimiterMask(final long word) {
long match = word ^ SEPARATOR_PATTERN;
return (match - 0x0101010101010101L) & ~match & 0x8080808080808080L;
}
private static final long SEPARATOR_PATTERN = 0x3B3B3B3B3B3B3B3BL;
private static final long DOT_BITS = 0x10101000;
private static final long MAGIC_MULTIPLIER = (100 * 0x1000000 + 10 * 0x10000 + 1);
// Takes a long and finds the bytes where this exact pattern is present.
// Cool bit manipulation technique: SWAR (SIMD as a Register).
private static long getDelimiterMask(final long word) {
final long match = word ^ SEPARATOR_PATTERN;
return (match - 0x0101010101010101L) & (~match & 0x8080808080808080L);
// I've put some brackets separating the first and second part, this is faster.
// Now they run simultaneous after 'match' is altered, instead of waiting on each other.
}
/**
* For case multiple hashes are equal (however unlikely) check the actual key (using longs)
*/
static boolean arrayEquals(final long[] a, final long[] b, final int length) {
for (int i = 0; i < length; i++) {
if (a[i] != b[i])
private static boolean memoryEqualsEntry(final long startAddress, final long[] entry, final long finalBytes, final int amountLong) {
for (int i = 0; i < (amountLong - 1); i++) {
int step = i << 3; // step by 8 bytes
if (UNSAFE.getLong(startAddress + step) != entry[i])
return false;
}
return true;
// If all previous 'whole' 8-packed byte-long values are equal
// We still need to check the final bytes that don't fit.
// and we've already calculated them for the hash.
return finalBytes == entry[amountLong - 1];
}
}