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armandino: minimise hash collisions + other improvements (#585)

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This commit is contained in:
Arman Sharif
2024-01-25 13:59:18 -08:00
committed by GitHub
parent 271bdfb032
commit d5cedd6a35
3 changed files with 79 additions and 53 deletions
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96
src/main/java/dev/morling/onebrc/CalculateAverage_armandino.java
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@@ -45,6 +45,7 @@ public class CalculateAverage_armandino {
private static final byte DOT = 46;
private static final byte MINUS = 45;
private static final byte ZERO_DIGIT = 48;
private static final int PRIME = 1117;
private static final Unsafe UNSAFE = getUnsafe();
public static void main(String[] args) throws Exception {
@@ -78,7 +79,7 @@ public class CalculateAverage_armandino {
byte b;
while ((b = UNSAFE.getByte(i++)) != SEMICOLON) {
keyHash = 31 * keyHash + b;
keyHash = PRIME * keyHash + b;
}
final int keyLength = (int) (i - keyAddress - 1);
@@ -114,13 +115,14 @@ public class CalculateAverage_armandino {
stats.sum += measurement;
stats.count++;
}
return map;
}
}
private static class Stats implements Comparable<Stats> {
private String key;
private final byte[] keyBytes;
private final long keyAddress;
private final int keyLength;
private final int keyHash;
private int min = Integer.MAX_VALUE;
@@ -129,17 +131,15 @@ public class CalculateAverage_armandino {
private long sum;
private Stats(long keyAddress, int keyLength, int keyHash) {
this.keyAddress = keyAddress;
this.keyLength = keyLength;
this.keyBytes = new byte[keyLength];
this.keyHash = keyHash;
for (int i = 0; i < keyLength; i++) {
keyBytes[i] = UNSAFE.getByte(keyAddress++);
}
}
String getKey() {
if (key == null) {
var keyBytes = new byte[keyLength];
UNSAFE.copyMemory(null, keyAddress, keyBytes, Unsafe.ARRAY_BYTE_BASE_OFFSET, keyLength);
key = new String(keyBytes, 0, keyLength, UTF_8);
}
return key;
@@ -230,37 +230,6 @@ public class CalculateAverage_armandino {
return Arrays.stream(table).filter(Objects::nonNull);
}
private void resize() {
var copy = new SimpleMap(table.length * 2);
for (Stats s : table) {
if (s != null) {
final int pos = (copy.table.length - 1) & s.keyHash;
int i = pos;
if (copy.table[i] == null) {
copy.table[i] = s;
continue;
}
while (i < copy.table.length && copy.table[i] != null) {
i++;
}
if (i == copy.table.length) {
i = pos;
while (i >= 0 && copy.table[i] != null) {
i--;
}
}
if (i < 0) {
// shouldn't happen because put() is called after increasing size
throw new IllegalStateException("table is full");
}
copy.table[i] = s;
}
}
table = copy.table;
}
Stats putStats(final int keyHash, final long keyAddress, final int keyLength) {
final int pos = (table.length - 1) & keyHash;
@@ -291,22 +260,49 @@ public class CalculateAverage_armandino {
return putStats(keyHash, keyAddress, keyLength);
}
private boolean keysEqual(Stats stats, long keyAddress, final int keyLength) {
if (stats.keyLength != keyLength) {
return false;
}
for (int i = 0; i < keyLength; i++) {
if (stats.keyBytes[i] != UNSAFE.getByte(keyAddress++)) {
return false;
}
}
return true;
}
private static Stats createAt(Stats[] table, long keyAddress, int keyLength, int key, int i) {
Stats stats = new Stats(keyAddress, keyLength, key);
table[i] = stats;
return stats;
}
private static boolean keysEqual(Stats stats, long keyAddress, final int keyLength) {
// credit: abeobk
long xsum = 0;
int n = keyLength & 0xF8;
for (int i = 0; i < n; i += 8) {
xsum |= (UNSAFE.getLong(stats.keyAddress + i) ^ UNSAFE.getLong(keyAddress + i));
}
return xsum == 0;
}
private void resize() {
var copy = new SimpleMap(table.length * 2);
for (Stats s : table) {
if (s != null) {
final int pos = (copy.table.length - 1) & s.keyHash;
int i = pos;
if (copy.table[i] == null) {
copy.table[i] = s;
continue;
}
while (i < copy.table.length && copy.table[i] != null) {
i++;
}
if (i == copy.table.length) {
i = pos;
while (i >= 0 && copy.table[i] != null) {
i--;
}
}
if (i < 0) {
// if we reach here it's a bug!
throw new IllegalStateException("table is full");
}
copy.table[i] = s;
}
}
table = copy.table;
}
}
}