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roman-r-m improved version (#368)

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* remove unneeded check

* slightly improved hash code perf

* Use unsafe to access memory + untangle the code a bit

* Adhoc cache that works a bit better

* Store station names as offset into the memory segment + length; slightly change how the hash is calculated
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Roman Musin 2024-01-13 10:46:52 +00:00 committed by GitHub
parent 062f424c10
commit 092132afe9
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 54 additions and 40 deletions
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94
src/main/java/dev/morling/onebrc/CalculateAverage_roman_r_m.java
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@ -15,11 +15,13 @@
*/
package dev.morling.onebrc;
import sun.misc.Unsafe;
import java.io.File;
import java.io.IOException;
import java.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.lang.foreign.ValueLayout;
import java.lang.reflect.Field;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.util.ArrayList;
@ -34,6 +36,8 @@ public class CalculateAverage_roman_r_m {
private static final String FILE = "./measurements.txt";
private static MemorySegment ms;
private static Unsafe UNSAFE;
// based on http://0x80.pl/notesen/2023-03-06-swar-find-any.html
static long hasZeroByte(long l) {
return ((l - 0x0101010101010101L) & ~(l) & 0x8080808080808080L);
@ -67,7 +71,11 @@ public class CalculateAverage_roman_r_m {
return start + i;
}
public static void main(String[] args) throws IOException {
public static void main(String[] args) throws Exception {
Field f = Unsafe.class.getDeclaredField("theUnsafe");
f.setAccessible(true);
UNSAFE = (Unsafe) f.get(null);
long fileSize = new File(FILE).length();
var channel = FileChannel.open(Paths.get(FILE));
@ -88,34 +96,29 @@ public class CalculateAverage_roman_r_m {
long offset = chunkStart;
while (offset < chunkEnd) {
long start = offset;
long pos;
long pos = -1;
if (!lastChunk || chunkEnd - offset >= 8) {
long next = ms.get(ValueLayout.JAVA_LONG_UNALIGNED, offset);
while ((pos = find(next, SEMICOLON_MASK)) < 0) {
offset += 8;
if (!lastChunk || fileSize - offset >= 8) {
next = ms.get(ValueLayout.JAVA_LONG_UNALIGNED, offset);
}
else {
while (ms.get(ValueLayout.JAVA_BYTE, offset + pos) != ';') {
pos++;
}
while (chunkEnd - offset >= 8) {
long next = UNSAFE.getLong(ms.address() + offset);
pos = find(next, SEMICOLON_MASK);
if (pos >= 0) {
offset += pos;
break;
}
}
}
else {
pos = 0;
while (ms.get(ValueLayout.JAVA_BYTE, offset + pos) != ';') {
pos++;
offset += 8;
}
}
offset += pos;
if (pos < 0) {
while (UNSAFE.getByte(ms.address() + offset++) != ';') {
}
offset--;
}
int len = (int) (offset - start);
// TODO can we not copy and use a reference into the memory segment to perform table lookup?
MemorySegment.copy(ms, ValueLayout.JAVA_BYTE, start, station.buf, 0, len);
station.offset = start;
station.len = len;
station.hash = 0;
@ -124,7 +127,7 @@ public class CalculateAverage_roman_r_m {
long val;
boolean neg;
if (!lastChunk || fileSize - offset >= 8) {
long encodedVal = ms.get(ValueLayout.JAVA_LONG_UNALIGNED, offset);
long encodedVal = UNSAFE.getLong(ms.address() + offset);
neg = (encodedVal & (byte) '-') == (byte) '-';
if (neg) {
encodedVal >>= 8;
@ -143,16 +146,16 @@ public class CalculateAverage_roman_r_m {
}
}
else {
neg = ms.get(ValueLayout.JAVA_BYTE, offset) == '-';
neg = UNSAFE.getByte(ms.address() + offset) == '-';
if (neg) {
offset++;
}
val = ms.get(ValueLayout.JAVA_BYTE, offset++) - '0';
val = UNSAFE.getByte(ms.address() + offset++) - '0';
byte b;
while ((b = ms.get(ValueLayout.JAVA_BYTE, offset++)) != '.') {
while ((b = UNSAFE.getByte(ms.address() + offset++)) != '.') {
val = val * 10 + (b - '0');
}
b = ms.get(ValueLayout.JAVA_BYTE, offset);
b = UNSAFE.getByte(ms.address() + offset);
val = val * 10 + (b - '0');
offset += 2;
}
@ -178,23 +181,22 @@ public class CalculateAverage_roman_r_m {
static final class ByteString {
private byte[] buf = new byte[100];
private long offset;
private int len = 0;
private int hash = 0;
@Override
public String toString() {
return new String(buf, 0, len);
var bytes = new byte[len];
MemorySegment.copy(ms, ValueLayout.JAVA_BYTE, offset, bytes, 0, len);
return new String(bytes, 0, len);
}
public ByteString copy() {
var copy = new ByteString();
copy.offset = this.offset;
copy.len = this.len;
copy.hash = this.hash;
if (copy.buf.length < this.buf.length) {
copy.buf = new byte[this.buf.length];
}
System.arraycopy(this.buf, 0, copy.buf, 0, this.len);
return copy;
}
@ -210,22 +212,34 @@ public class CalculateAverage_roman_r_m {
if (len != that.len)
return false;
// TODO use Vector
for (int i = 0; i < len; i++) {
if (buf[i] != that.buf[i]) {
int i = 0;
long base1 = ms.address() + offset;
long base2 = ms.address() + that.offset;
for (; i + 3 < len; i += 4) {
int i1 = UNSAFE.getInt(base1 + i);
int i2 = UNSAFE.getInt(base2 + i);
if (i1 != i2) {
return false;
}
}
for (; i < len; i++) {
byte i1 = UNSAFE.getByte(base1 + i);
byte i2 = UNSAFE.getByte(base2 + i);
if (i1 != i2) {
return false;
}
}
return true;
}
@Override
public int hashCode() {
if (hash == 0) {
for (int i = 0; i < len; i++) {
hash = 31 * hash + (buf[i] & 255);
}
// not sure why but it seems to be working a bit better
hash = UNSAFE.getInt(ms.address() + offset);
hash = hash >>> (8 * Math.max(0, 4 - len));
hash |= len;
}
return hash;
}