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Manually compute temperature value instead of using Long.parseLong

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Filip Hrisafov 2024-01-03 23:28:03 +01:00 committed by Gunnar Morling
parent f5f3a41045
commit 8c5aaf2db9
1 changed files with 14 additions and 8 deletions
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22
src/main/java/dev/morling/onebrc/CalculateAverage_filiphr.java
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@ -41,6 +41,7 @@ import java.util.stream.StreamSupport;
* Using big decimal and iterating the buffer once: 0m 20s
* Using long parse: 0m 11s
* Using array hash code for city key: 0m 7.1s
* Manually compute the value: 0m 6.8s
* <p>
* Using 21.0.1 Temurin with ShenandoahGC on Macbook (Intel) Pro
* `sdk use java 21.0.1-tem`
@ -156,10 +157,6 @@ public class CalculateAverage_filiphr {
Map<Integer, Measurement> measurements = HashMap.newHashMap(415);
int limit = bb.limit();
byte[] cityBuffer = new byte[128];
char[] charArray = new char[8];
CharBuffer charBuffer = CharBuffer.wrap(charArray);
charBuffer.clear();
charBuffer.position(0);
while (bb.position() < limit) {
int cityBufferIndex = 0;
@ -177,20 +174,29 @@ public class CalculateAverage_filiphr {
}
byte lastPositionByte = '\n';
int temperatureBufferIndex = 0;
boolean negative = false;
long value = 0;
while (bb.position() < limit) {
byte positionByte = bb.get();
if (positionByte == '\r' || positionByte == '\n') {
lastPositionByte = positionByte;
break;
}
else if (positionByte == '-') {
negative = true;
}
else if (positionByte != '.') {
charArray[temperatureBufferIndex++] = (char) positionByte;
// The 0 to 9 characters have an int value of 48 (for 0) to 57 (for 9)
// Therefore, in order to compute the digit we subtract with 48
int digit = positionByte - 48;
// We are computing the value by hand (in order to avoid iterating the index twice)
value = value * 10 + digit;
}
}
// Create the temperature
long value = Long.parseLong(charBuffer, 0, temperatureBufferIndex, 10);
if (negative) {
value = -value;
}
Measurement measurement = measurements.get(cityKey);
if (measurement == null) {