On Wed, 21 Jun 2023 10:11:09 GMT, 温绍锦 <d...@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:
>
> 8310502 : HEX256 initialization use constant values improved jvm startup
src/java.base/share/classes/java/lang/Long.java line 128:
> 126: 26209, 26210, 26211, 26212, 26213, 26214
> 127: };
> 128:
Can we perhaps have hex literals here? I think they are easier to visually
check than decimals.
static final char[] HEX256 = new char[]{
0x3030, 0x3031, 0x3032, 0x3033, 0x3034, 0x3035, 0x3036, 0x3037, ...
or
static final char[] HEX256 = new char[]{
0x30_30, 0x30_31, 0x30_32, 0x30_33, 0x30_34, 0x30_35, 0x30_36, 0x30_37,
...
src/java.base/share/classes/java/lang/Long.java line 492:
> 490: final char[] hex256 = HEX256;
> 491:
> 492: char i = hex256[((int) (msb >> 56)) & 255];
Masks are easier to read when expressed as hex literals.
char i = hex256[((int) (msb >> 56)) & 0xFF];
...
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/14578#discussion_r1236753357
PR Review Comment: https://git.openjdk.org/jdk/pull/14578#discussion_r1236753461
