Use SIMD for search for delimiter and name compare
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Thomas Wuerthinger
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GitHub
GitHub
parent
9e9e533401
commit
243388ad7b
@@ -25,29 +25,33 @@ import java.nio.channels.FileChannel.MapMode;
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import java.nio.charset.StandardCharsets;
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import java.nio.file.Path;
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import java.nio.file.StandardOpenOption;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.TreeMap;
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import java.util.*;
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import java.util.stream.IntStream;
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/**
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* Simple solution that memory maps the input file, then splits it into one segment per available core and uses
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* sun.misc.Unsafe to directly access the mapped memory.
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*
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* Runs in 0.92s on my Intel i9-13900K
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* Perf stats:
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* 65,004,666,383 cpu_core/cycles/
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* 71,141,249,972 cpu_atom/cycles/
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*/
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public class CalculateAverage_thomaswue {
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private static final String FILE = "./measurements.txt";
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// Holding the current result for a single city.
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private static class Result {
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int min;
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int max;
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short min;
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short max;
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long sum;
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int count;
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final long nameAddress;
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final int nameLength;
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private Result(long nameAddress, int nameLength, int value) {
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private Result(long nameAddress, int value) {
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this.nameAddress = nameAddress;
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this.nameLength = nameLength;
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this.min = value;
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this.max = value;
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this.min = (short) value;
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this.max = (short) value;
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this.sum = value;
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this.count = 1;
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}
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@@ -62,8 +66,8 @@ public class CalculateAverage_thomaswue {
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// Accumulate another result into this one.
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private void add(Result other) {
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min = Math.min(min, other.min);
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max = Math.max(max, other.max);
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min = (short) Math.min(min, other.min);
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max = (short) Math.max(max, other.max);
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sum += other.sum;
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count += other.count;
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}
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@@ -77,7 +81,7 @@ public class CalculateAverage_thomaswue {
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// Parallel processing of segments.
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List<HashMap<String, Result>> allResults = IntStream.range(0, chunks.length - 1).mapToObj(chunkIndex -> {
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HashMap<String, Result> cities = HashMap.newHashMap(1 << 10);
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Result[] results = new Result[1 << 14];
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Result[] results = new Result[1 << 18];
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parseLoop(chunks[chunkIndex], chunks[chunkIndex + 1], results, cities);
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return cities;
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}).parallel().toList();
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@@ -86,13 +90,10 @@ public class CalculateAverage_thomaswue {
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HashMap<String, Result> result = allResults.getFirst();
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for (int i = 1; i < allResults.size(); ++i) {
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for (Map.Entry<String, Result> entry : allResults.get(i).entrySet()) {
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Result current = result.get(entry.getKey());
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Result current = result.putIfAbsent(entry.getKey(), entry.getValue());
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if (current != null) {
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current.add(entry.getValue());
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}
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else {
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result.put(entry.getKey(), entry.getValue());
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}
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}
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}
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@@ -113,34 +114,46 @@ public class CalculateAverage_thomaswue {
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}
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}
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static boolean unsafeEquals(long aStart, long aLength, long bStart, long bLength) {
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if (aLength != bLength) {
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return false;
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}
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for (int i = 0; i < aLength; ++i) {
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if (UNSAFE.getByte(aStart + i) != UNSAFE.getByte(bStart + i)) {
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return false;
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}
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}
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return true;
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}
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private static void parseLoop(long chunkStart, long chunkEnd, Result[] results, HashMap<String, Result> cities) {
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long scanPtr = chunkStart;
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byte b;
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while (scanPtr < chunkEnd) {
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long nameAddress = scanPtr;
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int hash = 0;
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int hash = UNSAFE.getByte(scanPtr++);
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while ((b = UNSAFE.getByte(scanPtr++)) != ';') {
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hash += b;
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hash += hash << 10;
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hash ^= hash >> 6;
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// Skip first letter.
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scanPtr++;
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// Scan for ';' delimiter, always 4 bytes at a time.
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while (true) {
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int nextVal = UNSAFE.getInt(scanPtr);
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if ((nextVal & 0x3B) == 0x3B) {
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scanPtr++;
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break;
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}
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else if ((nextVal & 0x3B00) == 0x3B00) {
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scanPtr += 2;
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hash = hash ^ (nextVal & 0xFF);
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break;
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}
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else if ((nextVal & 0x3B0000) == 0x3B0000) {
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scanPtr += 3;
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hash = hash ^ (nextVal & 0xFFFF);
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break;
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}
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else if (((nextVal & 0x3B000000) == 0x3B000000)) {
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scanPtr += 4;
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hash = hash ^ (nextVal & 0xFFFFFF);
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break;
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}
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scanPtr += 4;
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hash = hash ^ nextVal;
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}
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int nameLength = (int) (scanPtr - 1 - nameAddress);
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hash = hash & (results.length - 1);
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// Save length of name for later.
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int nameLength = (int) (scanPtr - nameAddress - 1);
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// Parse number.
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int number;
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byte sign = UNSAFE.getByte(scanPtr++);
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if (sign == '-') {
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@@ -161,26 +174,53 @@ public class CalculateAverage_thomaswue {
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number = number * 10 + (UNSAFE.getByte(scanPtr++) - '0');
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}
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// Final calculation for index into hash table.
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int tableIndex = (((hash ^ (hash >>> 18)) & (results.length - 1)));
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while (true) {
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Result existingResult = results[hash];
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Result existingResult = results[tableIndex];
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if (existingResult == null) {
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Result r = new Result(nameAddress, nameLength, number);
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results[hash] = r;
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byte[] bytes = new byte[nameLength];
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UNSAFE.copyMemory(null, nameAddress, bytes, Unsafe.ARRAY_BYTE_BASE_OFFSET, nameLength);
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cities.put(new String(bytes, StandardCharsets.UTF_8), r);
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break;
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}
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else if (unsafeEquals(existingResult.nameAddress, existingResult.nameLength, nameAddress, nameLength)) {
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existingResult.min = Math.min(existingResult.min, number);
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existingResult.max = Math.max(existingResult.max, number);
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existingResult.sum += number;
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existingResult.count++;
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newEntry(results, cities, nameAddress, number, tableIndex, nameLength);
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break;
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}
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else {
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// Collision error, try next.
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hash = (hash + 1) & (results.length - 1);
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// Check for collision.
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boolean result = true;
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int i = 0;
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if ((long) nameLength >= 8) {
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if (UNSAFE.getLong(existingResult.nameAddress) != UNSAFE.getLong(nameAddress)) {
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result = false;
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}
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else {
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i += 8;
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}
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}
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else if ((long) nameLength >= 4) {
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if (UNSAFE.getInt(existingResult.nameAddress) != UNSAFE.getInt(nameAddress)) {
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result = false;
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}
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else {
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i += 4;
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}
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}
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if (result) {
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for (; i < (long) nameLength; ++i) {
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if (UNSAFE.getByte(existingResult.nameAddress + i) != UNSAFE.getByte(nameAddress + i)) {
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result = false;
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break;
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}
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}
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}
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if (result) {
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existingResult.min = (short) Math.min(existingResult.min, number);
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existingResult.max = (short) Math.max(existingResult.max, number);
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existingResult.sum += number;
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existingResult.count++;
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break;
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}
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else {
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// Collision error, try next.
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tableIndex = (tableIndex + 1) & (results.length - 1);
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}
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}
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}
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@@ -189,6 +229,14 @@ public class CalculateAverage_thomaswue {
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}
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}
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private static void newEntry(Result[] results, HashMap<String, Result> cities, long nameAddress, int number, int hash, int nameLength) {
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Result r = new Result(nameAddress, number);
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results[hash] = r;
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byte[] bytes = new byte[nameLength];
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UNSAFE.copyMemory(null, nameAddress, bytes, Unsafe.ARRAY_BYTE_BASE_OFFSET, nameLength);
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cities.put(new String(bytes, StandardCharsets.UTF_8), r);
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}
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private static long[] getSegments(int numberOfChunks) throws IOException {
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try (var fileChannel = FileChannel.open(Path.of(FILE), StandardOpenOption.READ)) {
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long fileSize = fileChannel.size();
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