richardstartin commented on pull request #7487:
URL: https://github.com/apache/pinot/pull/7487#issuecomment-927795364
Here's a quick comparison to show what's at stake here (I don't think the
benchmark is worth maintaining in this project). Note that I selected lengths
which aren't aligned to make sure slower tails of loops execute, which won't
happen on aligned inputs.
```java
@State(Scope.Benchmark)
public class BenchmarkByteArrayCompare {
@Param({"7", "31", "1023"})
int _length;
@Param("1")
int _offset;
private byte[] _left;
private byte[] _right;
@Setup(Level.Trial)
public void setup() {
_left = new byte[_length];
ThreadLocalRandom.current().nextBytes(_left);
_right = Arrays.copyOf(_left, _left.length);
_right[_right.length - _offset] = (byte) ~_left[_left.length - _offset];
}
@Benchmark
public int compare() {
return ByteArray.compare(_left, _right);
}
}
```
```
Benchmark (_length) (_offset) Mode Cnt Score
Error Units
BenchmarkByteArrayCompare.compare 7 1 avgt 5 5.942
± 0.048 ns/op
BenchmarkByteArrayCompare.compare 31 1 avgt 5 15.298
± 1.040 ns/op
BenchmarkByteArrayCompare.compare 1023 1 avgt 5 320.390
± 1.262 ns/op
Benchmark (_length) (_offset) Mode Cnt Score
Error Units
BenchmarkByteArrayCompare.compare 7 1 avgt 5 7.913 ±
0.174 ns/op
BenchmarkByteArrayCompare.compare 31 1 avgt 5 8.351 ±
0.016 ns/op
BenchmarkByteArrayCompare.compare 1023 1 avgt 5 22.765 ±
1.566 ns/op
```
For inputs shorter than 8 bytes, there is a small setup cost of the order of
1ns, but for larger inputs the improvement is huge.
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