On Tue, 12 Sep 2023 19:23:13 GMT, Roger Riggs <rri...@openjdk.org> wrote:
>> 温绍锦 has updated the pull request with a new target base due to a merge or a >> rebase. The pull request now contains 19 commits: >> >> - merge from master >> - Merge branch 'master' into optimization_for_uuid_to_string >> >> # Conflicts: >> # src/java.base/share/classes/java/util/UUID.java >> # src/java.base/share/classes/jdk/internal/util/HexDigits.java >> - lo | hi => hi | lo >> - add DIGITS description >> - reversed how & hi >> - Merge branch 'master' into optimization_for_uuid_to_string >> - remove redundant parentheses >> - fix java doc, big-endian -> little-endian >> - Merge branch 'master' into optimization_for_uuid_to_string >> - use ByteArrayLittleEndian >> - ... and 9 more: https://git.openjdk.org/jdk/compare/e0845163...4f6ed3e6 > > src/java.base/share/classes/jdk/internal/util/HexDigits.java line 112: > >> 110: | (DIGITS[b1 & 0xff] << 16) >> 111: | (((long) DIGITS[b2 & 0xff]) << 32) >> 112: | (((long) DIGITS[b3 & 0xff]) << 48); > > Can you reverse the order of these source lines to put the shifts of the > higher order bits before the lower order bit shifts. `3333222211110000`. Its > easier to understand where the bits end up in the long. > The rest of the change is better focused. if change packDigits order, performance will be slow, I don't know why yet. The following is the data running on MacBookPro M1 Max : make test TEST="micro:java.util.UUIDBench.toString" Benchmark (size) Mode Cnt Score Error Units (current order) UUIDBench.toString 20000 thrpt 15 96.396 ? 0.946 ops/us Benchmark (size) Mode Cnt Score Error Units (change packDigits order) UUIDBench.toString 20000 thrpt 15 86.496 ? 0.542 ops/us ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14745#discussion_r1323682688
