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edge-case in hashing fixed (#459)

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also a bunch of smaller improvements
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Jaromir Hamala 2024-01-17 18:28:03 +01:00 committed by GitHub
parent 77872e197d
commit 927880b97e
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2 changed files with 153 additions and 154 deletions
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2
calculate_average_jerrinot.sh
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@ -17,5 +17,5 @@
# -XX:+UnlockDiagnosticVMOptions -XX:PrintAssemblyOptions=intel -XX:CompileCommand=print,*.CalculateAverage_mtopolnik::recordMeasurementAndAdvanceCursor" # -XX:+UnlockDiagnosticVMOptions -XX:PrintAssemblyOptions=intel -XX:CompileCommand=print,*.CalculateAverage_mtopolnik::recordMeasurementAndAdvanceCursor"
# -XX:InlineSmallCode=10000 -XX:-TieredCompilation -XX:CICompilerCount=2 -XX:CompileThreshold=1000\ # -XX:InlineSmallCode=10000 -XX:-TieredCompilation -XX:CICompilerCount=2 -XX:CompileThreshold=1000\
java --enable-preview \ java -XX:+UseParallelGC --enable-preview \
--class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_jerrinot --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_jerrinot

289
src/main/java/dev/morling/onebrc/CalculateAverage_jerrinot.java
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@ -22,15 +22,24 @@ import java.io.RandomAccessFile;
import java.lang.foreign.Arena; import java.lang.foreign.Arena;
import java.lang.reflect.Field; import java.lang.reflect.Field;
import java.nio.channels.FileChannel.MapMode; import java.nio.channels.FileChannel.MapMode;
import java.util.Map; import java.util.*;
import java.util.TreeMap;
/**
* I figured out it would be very hard to win the main competition of the One Billion Rows Challenge.
* but I think this code has a good chance to win a special prize for the Ugliest Solution ever! :)
*
* Anyway, if you can make sense out of not exactly idiomatic Java code, and you enjoy pushing performance limits
* then QuestDB - the fastest open-source time-series database - is hiring: https://questdb.io/careers/core-database-engineer/
*
*/
public class CalculateAverage_jerrinot { public class CalculateAverage_jerrinot {
private static final Unsafe UNSAFE = unsafe(); private static final Unsafe UNSAFE = unsafe();
private static final String MEASUREMENTS_TXT = "measurements.txt"; private static final String MEASUREMENTS_TXT = "measurements.txt";
// todo: with hyper-threading enable we would be better of with availableProcessors / 2; // todo: with hyper-threading enable we would be better of with availableProcessors / 2;
// todo: validate the testing env. params. // todo: validate the testing env. params.
private static final int THREAD_COUNT = Runtime.getRuntime().availableProcessors(); private static final int THREAD_COUNT = Runtime.getRuntime().availableProcessors();
// private static final int THREAD_COUNT = 4;
private static final long SEPARATOR_PATTERN = 0x3B3B3B3B3B3B3B3BL; private static final long SEPARATOR_PATTERN = 0x3B3B3B3B3B3B3B3BL;
private static Unsafe unsafe() { private static Unsafe unsafe() {
@ -72,7 +81,7 @@ public class CalculateAverage_jerrinot {
Processor[] processors = new Processor[THREAD_COUNT]; Processor[] processors = new Processor[THREAD_COUNT];
Thread[] threads = new Thread[THREAD_COUNT]; Thread[] threads = new Thread[THREAD_COUNT];
for (int i = 0; i < THREAD_COUNT; i++) { for (int i = 0; i < THREAD_COUNT - 1; i++) {
long startA = chunkStartOffsets[i * chunkPerThread]; long startA = chunkStartOffsets[i * chunkPerThread];
long endA = chunkStartOffsets[i * chunkPerThread + 1]; long endA = chunkStartOffsets[i * chunkPerThread + 1];
long startB = chunkStartOffsets[i * chunkPerThread + 1]; long startB = chunkStartOffsets[i * chunkPerThread + 1];
@ -89,8 +98,22 @@ public class CalculateAverage_jerrinot {
thread.start(); thread.start();
} }
int ownIndex = THREAD_COUNT - 1;
long startA = chunkStartOffsets[ownIndex * chunkPerThread];
long endA = chunkStartOffsets[ownIndex * chunkPerThread + 1];
long startB = chunkStartOffsets[ownIndex * chunkPerThread + 1];
long endB = chunkStartOffsets[ownIndex * chunkPerThread + 2];
long startC = chunkStartOffsets[ownIndex * chunkPerThread + 2];
long endC = chunkStartOffsets[ownIndex * chunkPerThread + 3];
long startD = chunkStartOffsets[ownIndex * chunkPerThread + 3];
long endD = chunkStartOffsets[ownIndex * chunkPerThread + 4];
Processor processor = new Processor(startA, endA, startB, endB, startC, endC, startD, endD);
processor.run();
var accumulator = new TreeMap<String, Processor.StationStats>(); var accumulator = new TreeMap<String, Processor.StationStats>();
for (int i = 0; i < THREAD_COUNT; i++) { processor.accumulateStatus(accumulator);
for (int i = 0; i < THREAD_COUNT - 1; i++) {
Thread t = threads[i]; Thread t = threads[i];
t.join(); t.join();
processors[i].accumulateStatus(accumulator); processors[i].accumulateStatus(accumulator);
@ -131,7 +154,7 @@ public class CalculateAverage_jerrinot {
private static class Processor implements Runnable { private static class Processor implements Runnable {
private static final int MAP_SLOT_COUNT = ceilPow2(10000); private static final int MAP_SLOT_COUNT = ceilPow2(10000);
private static final int STATION_MAX_NAME_BYTES = 104; private static final int STATION_MAX_NAME_BYTES = 120;
private static final long COUNT_OFFSET = 0; private static final long COUNT_OFFSET = 0;
private static final long MIN_OFFSET = 4; private static final long MIN_OFFSET = 4;
@ -162,23 +185,16 @@ public class CalculateAverage_jerrinot {
private long endC; private long endC;
private long cursorD; private long cursorD;
private long endD; private long endD;
private long maskA;
private long maskB; // private long maxClusterLen;
private long maskC;
private long maskD;
// credit: merykitty // credit: merykitty
private long parseAndStoreTemperature(long startCursor, long baseEntryPtr) { private long parseAndStoreTemperature(long startCursor, long baseEntryPtr, long word) {
long word = UNSAFE.getLong(startCursor); // long word = UNSAFE.getLong(startCursor);
final long negateda = ~word;
final int dotPos = Long.numberOfTrailingZeros(negateda & 0x10101000);
final long signed = (negateda << 59) >> 63;
final long removeSignMask = ~(signed & 0xFF);
final long digits = ((word & removeSignMask) << (28 - dotPos)) & 0x0F000F0F00L;
final long absValue = ((digits * 0x640a0001) >>> 32) & 0x3FF;
final int temperature = (int) ((absValue ^ signed) - signed);
long countPtr = baseEntryPtr + COUNT_OFFSET; long countPtr = baseEntryPtr + COUNT_OFFSET;
int cnt = UNSAFE.getInt(countPtr);
UNSAFE.putInt(countPtr, cnt + 1);
long minPtr = baseEntryPtr + MIN_OFFSET; long minPtr = baseEntryPtr + MIN_OFFSET;
long maxPtr = baseEntryPtr + MAX_OFFSET; long maxPtr = baseEntryPtr + MAX_OFFSET;
long sumPtr = baseEntryPtr + SUM_OFFSET; long sumPtr = baseEntryPtr + SUM_OFFSET;
@ -186,16 +202,23 @@ public class CalculateAverage_jerrinot {
int min = UNSAFE.getInt(minPtr); int min = UNSAFE.getInt(minPtr);
int max = UNSAFE.getInt(maxPtr); int max = UNSAFE.getInt(maxPtr);
long sum = UNSAFE.getLong(sumPtr); long sum = UNSAFE.getLong(sumPtr);
// try if min/max intrinsics are paying off
// maybe braching is better? the branch is becoming more predictable with final long negateda = ~word;
// each new sample. final int dotPos = Long.numberOfTrailingZeros(negateda & 0x10101000);
max = Math.max(max, temperature); final long signed = (negateda << 59) >> 63;
min = Math.min(min, temperature); final long removeSignMask = ~(signed & 0xFF);
final long digits = ((word & removeSignMask) << (28 - dotPos)) & 0x0F000F0F00L;
final long absValue = ((digits * 0x640a0001) >>> 32) & 0x3FF;
final int temperature = (int) ((absValue ^ signed) - signed);
sum += temperature; sum += temperature;
UNSAFE.putInt(countPtr, UNSAFE.getInt(countPtr) + 1);
UNSAFE.putInt(minPtr, min);
UNSAFE.putInt(maxPtr, max);
UNSAFE.putLong(sumPtr, sum); UNSAFE.putLong(sumPtr, sum);
if (temperature > max) {
UNSAFE.putInt(maxPtr, temperature);
}
if (temperature < min) {
UNSAFE.putInt(minPtr, temperature);
}
return startCursor + (dotPos / 8) + 3; return startCursor + (dotPos / 8) + 3;
} }
@ -227,13 +250,13 @@ public class CalculateAverage_jerrinot {
int count = UNSAFE.getInt(baseAddress + COUNT_OFFSET); int count = UNSAFE.getInt(baseAddress + COUNT_OFFSET);
long sum = UNSAFE.getLong(baseAddress + SUM_OFFSET); long sum = UNSAFE.getLong(baseAddress + SUM_OFFSET);
// todo: lambdas bootstrap probably cost us var v = accumulator.get(name);
accumulator.compute(name, (_, v) -> {
if (v == null) { if (v == null) {
return new StationStats(min, max, count, sum); accumulator.put(name, new StationStats(min, max, count, sum));
}
else {
accumulator.put(name, new StationStats(Math.min(v.min, min), Math.max(v.max, max), v.count + count, v.sum + sum));
} }
return new StationStats(Math.min(v.min, min), Math.max(v.max, max), v.count + count, v.sum + sum);
});
} }
} }
@ -260,11 +283,22 @@ public class CalculateAverage_jerrinot {
private void doTail() { private void doTail() {
// todo: we would be probably better of without all that code dup. ("compilers hates him!") // todo: we would be probably better of without all that code dup. ("compilers hates him!")
// System.out.println("done ILP"); // System.out.println("done ILP");
doOne(cursorA, endA);
// System.out.println("done A");
doOne(cursorB, endB);
// System.out.println("done B");
doOne(cursorC, endC);
// System.out.println("done C");
doOne(cursorD, endD);
// System.out.println("done D");
}
private void doOne(long cursorA, long endA) {
while (cursorA < endA) { while (cursorA < endA) {
long startA = cursorA; long startA = cursorA;
long delimiterWordA = UNSAFE.getLong(cursorA); long delimiterWordA = UNSAFE.getLong(cursorA);
long hashA = 0; long hashA = 0;
maskA = getDelimiterMask(delimiterWordA); long maskA = getDelimiterMask(delimiterWordA);
while (maskA == 0) { while (maskA == 0) {
hashA ^= delimiterWordA; hashA ^= delimiterWordA;
cursorA += 8; cursorA += 8;
@ -273,81 +307,15 @@ public class CalculateAverage_jerrinot {
} }
final int delimiterByteA = Long.numberOfTrailingZeros(maskA); final int delimiterByteA = Long.numberOfTrailingZeros(maskA);
final long semicolonA = cursorA + (delimiterByteA >> 3); final long semicolonA = cursorA + (delimiterByteA >> 3);
final long maskedWordA = delimiterWordA & ((maskA >>> 7) - 1); final long maskedWordA = delimiterWordA & ((maskA - 1) ^ maskA) >>> 8;
hashA ^= maskedWordA; hashA ^= maskedWordA;
int intHashA = (int) (hashA ^ (hashA >> 32)); int intHashA = (int) (hashA ^ (hashA >> 32));
intHashA = intHashA ^ (intHashA >> 17); intHashA = intHashA ^ (intHashA >> 17);
long baseEntryPtrA = getOrCreateEntryBaseOffset(semicolonA, startA, intHashA, maskedWordA); long baseEntryPtrA = getOrCreateEntryBaseOffset(semicolonA, startA, intHashA, maskedWordA);
cursorA = parseAndStoreTemperature(semicolonA + 1, baseEntryPtrA); long temperatureWordA = UNSAFE.getLong(semicolonA + 1);
cursorA = parseAndStoreTemperature(semicolonA + 1, baseEntryPtrA, temperatureWordA);
} }
// System.out.println("done A");
while (cursorB < endB) {
long startB = cursorB;
long delimiterWordB = UNSAFE.getLong(cursorB);
long hashB = 0;
maskB = getDelimiterMask(delimiterWordB);
while (maskB == 0) {
hashB ^= delimiterWordB;
cursorB += 8;
delimiterWordB = UNSAFE.getLong(cursorB);
maskB = getDelimiterMask(delimiterWordB);
}
final int delimiterByteB = Long.numberOfTrailingZeros(maskB);
final long semicolonB = cursorB + (delimiterByteB >> 3);
final long maskedWordB = delimiterWordB & ((maskB >>> 7) - 1);
hashB ^= maskedWordB;
int intHashB = (int) (hashB ^ (hashB >> 32));
intHashB = intHashB ^ (intHashB >> 17);
long baseEntryPtrB = getOrCreateEntryBaseOffset(semicolonB, startB, intHashB, maskedWordB);
cursorB = parseAndStoreTemperature(semicolonB + 1, baseEntryPtrB);
}
// System.out.println("done B");
while (cursorC < endC) {
long startC = cursorC;
long delimiterWordC = UNSAFE.getLong(cursorC);
long hashC = 0;
maskC = getDelimiterMask(delimiterWordC);
while (maskC == 0) {
hashC ^= delimiterWordC;
cursorC += 8;
delimiterWordC = UNSAFE.getLong(cursorC);
maskC = getDelimiterMask(delimiterWordC);
}
final int delimiterByteC = Long.numberOfTrailingZeros(maskC);
final long semicolonC = cursorC + (delimiterByteC >> 3);
final long maskedWordC = delimiterWordC & ((maskC >>> 7) - 1);
hashC ^= maskedWordC;
int intHashC = (int) (hashC ^ (hashC >> 32));
intHashC = intHashC ^ (intHashC >> 17);
long baseEntryPtrC = getOrCreateEntryBaseOffset(semicolonC, startC, intHashC, maskedWordC);
cursorC = parseAndStoreTemperature(semicolonC + 1, baseEntryPtrC);
}
// System.out.println("done C");
while (cursorD < endD) {
long startD = cursorD;
long delimiterWordD = UNSAFE.getLong(cursorD);
long hashD = 0;
maskD = getDelimiterMask(delimiterWordD);
while (maskD == 0) {
hashD ^= delimiterWordD;
cursorD += 8;
delimiterWordD = UNSAFE.getLong(cursorD);
maskD = getDelimiterMask(delimiterWordD);
}
final int delimiterByteD = Long.numberOfTrailingZeros(maskD);
final long semicolonD = cursorD + (delimiterByteD >> 3);
final long maskedWordD = delimiterWordD & ((maskD >>> 7) - 1);
hashD ^= maskedWordD;
int intHashD = (int) (hashD ^ (hashD >> 32));
intHashD = intHashD ^ (intHashD >> 17);
long baseEntryPtrD = getOrCreateEntryBaseOffset(semicolonD, startD, intHashD, maskedWordD);
cursorD = parseAndStoreTemperature(semicolonD + 1, baseEntryPtrD);
}
// System.out.println("done D");
} }
@Override @Override
@ -359,10 +327,14 @@ public class CalculateAverage_jerrinot {
long startC = cursorC; long startC = cursorC;
long startD = cursorD; long startD = cursorD;
long delimiterWordA = UNSAFE.getLong(cursorA); long currentWordA = UNSAFE.getLong(startA);
long delimiterWordB = UNSAFE.getLong(cursorB); // long delimiterWordA2 = UNSAFE.getLong(startA + 8);
long delimiterWordC = UNSAFE.getLong(cursorC); long currentWordB = UNSAFE.getLong(startB);
long delimiterWordD = UNSAFE.getLong(cursorD); // long delimiterWordB2 = UNSAFE.getLong(startB + 8);
long currentWordC = UNSAFE.getLong(startC);
// long delimiterWordCa = UNSAFE.getLong(startC + 8);
long currentWordD = UNSAFE.getLong(startD);
// long delimiterWordD2 = UNSAFE.getLong(startD + 8);
long hashA = 0; long hashA = 0;
long hashB = 0; long hashB = 0;
@ -370,58 +342,62 @@ public class CalculateAverage_jerrinot {
long hashD = 0; long hashD = 0;
// credits for the hashing idea: royvanrijn // credits for the hashing idea: royvanrijn
maskA = getDelimiterMask(delimiterWordA); long maskA = getDelimiterMask(currentWordA);
while (maskA == 0) { while (maskA == 0) {
hashA ^= delimiterWordA; hashA ^= currentWordA;
cursorA += 8; cursorA += 8;
delimiterWordA = UNSAFE.getLong(cursorA); currentWordA = UNSAFE.getLong(cursorA);
maskA = getDelimiterMask(delimiterWordA); maskA = getDelimiterMask(currentWordA);
} }
final int delimiterByteA = Long.numberOfTrailingZeros(maskA); final int delimiterByteA = Long.numberOfTrailingZeros(maskA);
final long semicolonA = cursorA + (delimiterByteA >> 3); final long semicolonA = cursorA + (delimiterByteA >> 3);
final long maskedWordA = delimiterWordA & ((maskA >>> 7) - 1); long temperatureWordA = UNSAFE.getLong(semicolonA + 1);
final long maskedWordA = currentWordA & ((maskA - 1) ^ maskA) >>> 8;
hashA ^= maskedWordA; hashA ^= maskedWordA;
int intHashA = (int) (hashA ^ (hashA >> 32)); int intHashA = (int) (hashA ^ (hashA >> 32));
intHashA = intHashA ^ (intHashA >> 17); intHashA = intHashA ^ (intHashA >> 17);
maskB = getDelimiterMask(delimiterWordB); long maskB = getDelimiterMask(currentWordB);
while (maskB == 0) { while (maskB == 0) {
hashB ^= delimiterWordB; hashB ^= currentWordB;
cursorB += 8; cursorB += 8;
delimiterWordB = UNSAFE.getLong(cursorB); currentWordB = UNSAFE.getLong(cursorB);
maskB = getDelimiterMask(delimiterWordB); maskB = getDelimiterMask(currentWordB);
} }
final int delimiterByteB = Long.numberOfTrailingZeros(maskB); final int delimiterByteB = Long.numberOfTrailingZeros(maskB);
final long semicolonB = cursorB + (delimiterByteB >> 3); final long semicolonB = cursorB + (delimiterByteB >> 3);
final long maskedWordB = delimiterWordB & ((maskB >>> 7) - 1); long temperatureWordB = UNSAFE.getLong(semicolonB + 1);
final long maskedWordB = currentWordB & ((maskB - 1) ^ maskB) >>> 8;
hashB ^= maskedWordB; hashB ^= maskedWordB;
int intHashB = (int) (hashB ^ (hashB >> 32)); int intHashB = (int) (hashB ^ (hashB >> 32));
intHashB = intHashB ^ (intHashB >> 17); intHashB = intHashB ^ (intHashB >> 17);
maskC = getDelimiterMask(delimiterWordC); long maskC = getDelimiterMask(currentWordC);
while (maskC == 0) { while (maskC == 0) {
hashC ^= delimiterWordC; hashC ^= currentWordC;
cursorC += 8; cursorC += 8;
delimiterWordC = UNSAFE.getLong(cursorC); currentWordC = UNSAFE.getLong(cursorC);
maskC = getDelimiterMask(delimiterWordC); maskC = getDelimiterMask(currentWordC);
} }
final int delimiterByteC = Long.numberOfTrailingZeros(maskC); final int delimiterByteC = Long.numberOfTrailingZeros(maskC);
final long semicolonC = cursorC + (delimiterByteC >> 3); final long semicolonC = cursorC + (delimiterByteC >> 3);
final long maskedWordC = delimiterWordC & ((maskC >>> 7) - 1); long temperatureWordC = UNSAFE.getLong(semicolonC + 1);
final long maskedWordC = currentWordC & ((maskC - 1) ^ maskC) >>> 8;
hashC ^= maskedWordC; hashC ^= maskedWordC;
int intHashC = (int) (hashC ^ (hashC >> 32)); int intHashC = (int) (hashC ^ (hashC >> 32));
intHashC = intHashC ^ (intHashC >> 17); intHashC = intHashC ^ (intHashC >> 17);
maskD = getDelimiterMask(delimiterWordD); long maskD = getDelimiterMask(currentWordD);
while (maskD == 0) { while (maskD == 0) {
hashD ^= delimiterWordD; hashD ^= currentWordD;
cursorD += 8; cursorD += 8;
delimiterWordD = UNSAFE.getLong(cursorD); currentWordD = UNSAFE.getLong(cursorD);
maskD = getDelimiterMask(delimiterWordD); maskD = getDelimiterMask(currentWordD);
} }
final int delimiterByteD = Long.numberOfTrailingZeros(maskD); final int delimiterByteD = Long.numberOfTrailingZeros(maskD);
final long semicolonD = cursorD + (delimiterByteD >> 3); final long semicolonD = cursorD + (delimiterByteD >> 3);
final long maskedWordD = delimiterWordD & ((maskD >>> 7) - 1); long temperatureWordD = UNSAFE.getLong(semicolonD + 1);
final long maskedWordD = currentWordD & ((maskD - 1) ^ maskD) >>> 8;
hashD ^= maskedWordD; hashD ^= maskedWordD;
int intHashD = (int) (hashD ^ (hashD >> 32)); int intHashD = (int) (hashD ^ (hashD >> 32));
intHashD = intHashD ^ (intHashD >> 17); intHashD = intHashD ^ (intHashD >> 17);
@ -431,51 +407,74 @@ public class CalculateAverage_jerrinot {
long baseEntryPtrC = getOrCreateEntryBaseOffset(semicolonC, startC, intHashC, maskedWordC); long baseEntryPtrC = getOrCreateEntryBaseOffset(semicolonC, startC, intHashC, maskedWordC);
long baseEntryPtrD = getOrCreateEntryBaseOffset(semicolonD, startD, intHashD, maskedWordD); long baseEntryPtrD = getOrCreateEntryBaseOffset(semicolonD, startD, intHashD, maskedWordD);
cursorA = parseAndStoreTemperature(semicolonA + 1, baseEntryPtrA); cursorA = parseAndStoreTemperature(semicolonA + 1, baseEntryPtrA, temperatureWordA);
cursorB = parseAndStoreTemperature(semicolonB + 1, baseEntryPtrB); cursorB = parseAndStoreTemperature(semicolonB + 1, baseEntryPtrB, temperatureWordB);
cursorC = parseAndStoreTemperature(semicolonC + 1, baseEntryPtrC); cursorC = parseAndStoreTemperature(semicolonC + 1, baseEntryPtrC, temperatureWordC);
cursorD = parseAndStoreTemperature(semicolonD + 1, baseEntryPtrD); cursorD = parseAndStoreTemperature(semicolonD + 1, baseEntryPtrD, temperatureWordD);
} }
doTail(); doTail();
} }
private long getOrCreateEntryBaseOffset(long semicolonA, long startA, int intHashA, long maskedWordA) { private long getOrCreateEntryBaseOffset(long semicolonA, long startA, int intHashA, long maskedWordA) {
int lenA = (int) (semicolonA - startA); // hashSet.add(intHashA);
long lenLong = semicolonA - startA;
int lenA = (int) lenLong;
// assert lenA != 0;
// byte[] nameArr = new byte[lenA];
// for (int i = 0; i < lenA; i++) {
// nameArr[i] = UNSAFE.getByte(startA + i);
// }
// String nameStr = new String(nameArr);
// Integer oldHash = nameToHash.put(nameStr, intHashA);
// assert oldHash == null || oldHash == intHashA : "name: " + nameStr + ", old hash = " + oldHash + ", new hash = " + intHashA;
long mapIndexA = intHashA & MAP_MASK; long mapIndexA = intHashA & MAP_MASK;
// long clusterLen = 0;
for (;;) { for (;;) {
long basePtr = mapIndexA * MAP_ENTRY_SIZE_BYTES + map; long basePtr = mapIndexA * MAP_ENTRY_SIZE_BYTES + map;
long lenPtr = basePtr + LEN_OFFSET; long lenPtr = basePtr + LEN_OFFSET;
int len = UNSAFE.getInt(lenPtr); int len = UNSAFE.getInt(lenPtr);
if (len == 0) { if (len == lenA) {
if (nameMatch(startA, maskedWordA, basePtr, lenLong)) {
// if (clusterLen > maxClusterLen) {
// maxClusterLen = clusterLen;
// System.out.println("max cluster len: " + clusterLen);
// }
return basePtr;
}
}
else if (len == 0) {
// todo: uncommon branch maybe? // todo: uncommon branch maybe?
// empty slot // empty slot
UNSAFE.copyMemory(semicolonA - lenA, basePtr + NAME_OFFSET, lenA); UNSAFE.copyMemory(semicolonA - lenA, basePtr + NAME_OFFSET, lenA);
UNSAFE.putInt(lenPtr, lenA); UNSAFE.putInt(lenPtr, lenA);
// todo: this could be a single putLong()
UNSAFE.putInt(basePtr + MAX_OFFSET, Integer.MIN_VALUE); UNSAFE.putInt(basePtr + MAX_OFFSET, Integer.MIN_VALUE);
UNSAFE.putInt(basePtr + MIN_OFFSET, Integer.MAX_VALUE); UNSAFE.putInt(basePtr + MIN_OFFSET, Integer.MAX_VALUE);
return basePtr; return basePtr;
} }
if (len == lenA) { mapIndexA = ++mapIndexA & MAP_MASK;
boolean match = true; // clusterLen++;
}
}
private static boolean nameMatch(long startA, long maskedWordA, long basePtr, long len) {
long namePtr = basePtr + NAME_OFFSET; long namePtr = basePtr + NAME_OFFSET;
int fullLen = (len >> 3) << 3; long fullLen = len & ~7L;
long offset; long offset;
// todo: this is worth exploring further. // todo: this is worth exploring further.
// @mtopolnik has an interesting algo with 2 unconditioned long loads: this is sufficient // @mtopolnik has an interesting algo with 2 unconditioned long loads: this is sufficient
// for majority of names. so we would be left with just a single branch which is almost never taken? // for majority of names. so we would be left with just a single branch which is almost never taken?
for (offset = 0; offset < fullLen; offset += 8) { for (offset = 0; offset < fullLen; offset += 8) {
match &= (UNSAFE.getLong(startA + offset) == UNSAFE.getLong(namePtr + offset)); if (UNSAFE.getLong(startA + offset) != UNSAFE.getLong(namePtr + offset)) {
return false;
}
} }
long maskedWordInMap = UNSAFE.getLong(namePtr + offset); long maskedWordInMap = UNSAFE.getLong(namePtr + fullLen);
match &= (maskedWordInMap == maskedWordA); return (maskedWordInMap == maskedWordA);
if (match) {
return basePtr;
}
}
mapIndexA = ++mapIndexA & MAP_MASK;
}
} }
} }