RFR: JDK-8310502 : Optimization for j.l.Long.fastUUID() [v13]

[Glavo]

On Thu, 22 Jun 2023 10:13:18 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> By optimizing the implementation of java.lang.Long#fastUUID, the performance of the java.util.UUID#toString method can be significantly improved.
>> 
>> The following are the test results of JMH: 
>> 
>> Benchmark                     Mode  Cnt      Score      Error   Units
>> UUIDUtilsBenchmark.new       thrpt    5  92676.550 ±  292.213  ops/ms
>> UUIDUtilsBenchmark.original  thrpt    5  37040.165 ± 1023.532  ops/ms
>
> 温绍锦 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   use ByteArray & simplify code

src/java.base/share/classes/java/lang/Long.java line 492:

> 490:             ByteArray.setChar(buf, 30, i13);
> 491:             ByteArray.setChar(buf, 32, i14);
> 492:             ByteArray.setChar(buf, 34, i15);

Suggestion:

            ByteArray.setLong(buf, 0, ((long) i0 << 48) | ((long) i1 << 32) | ((long) i2 << 16) | i3);
            buf[8] = '-';
            ByteArray.setInt(buf, 9, (i4 << 16) | i5);
            buf[13] = '-';
            ByteArray.setInt(buf, 14, (i6 << 16) | i7);
            buf[18] = '-';
            ByteArray.setInt(buf, 19, (i8 << 16) | i9);
            buf[23] = '-';
            ByteArray.setLong(buf, 24, ((long) i10 << 48) | ((long) i11 << 32) | ((long) i12 << 16) | i13);
            ByteArray.setInt(buf, 32, (i14 << 16) | i15);


JMH Result:


  Benchmark   Mode  Cnt      Score     Error   Units
- UUID.test  thrpt    5  87196.091 ± 492.129  ops/ms
+ UUID.test  thrpt    5  99197.287 ± 925.266  ops/ms

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/14578#discussion_r1238363498