RFR: 8347009: Speed up parseInt and parseLong [v13]
Raffaello Giulietti
rgiulietti at openjdk.org
Tue Feb 4 10:38:18 UTC 2025
On Sat, 1 Feb 2025 10:07:25 GMT, Shaojin Wen <swen at openjdk.org> wrote:
>> This is an optimization for decimal Integer.parseInt and Long.parseLong, which improves performance by about 10%. The optimization includes:
>> 1. Improve performance by parsing 2 numbers at a time, which has performance improvements for numbers with length >= 3.
>> 2. It uses charAt(0) for the first number. Assuming that the optimization can eliminate boundary checks, this will be more friendly to parsing numbers with length 1.
>> 3. It removes the reliance on the Character.digit method and eliminates the reliance on the CharacterDataLatin1#DIGITS cache array, which avoids performance degradation caused by cache misses.
>
> Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 29 commits:
>
> - Merge remote-tracking branch 'upstream/master' into optim_parse_int_long_202501
>
> # Conflicts:
> # src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
> - multiply 10
> - copyright
> - error message
> - Merge remote-tracking branch 'upstream/master' into optim_parse_int_long_202501
>
> # Conflicts:
> # src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
> - use &
> - from @rgiulietti
> - remove unused
> - Update src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
>
> Co-authored-by: Chen Liang <liach at openjdk.org>
> - vector digit2
> - ... and 19 more: https://git.openjdk.org/jdk/compare/651ac3cc...1fb40bb9
src/java.base/share/classes/java/lang/Integer.java line 525:
> 523: return parseInt0(s, radix);
> 524: }
> 525: int fc = value[0];
Suggestion:
/* Accumulating negatively avoids surprises near MAX_VALUE */
int fc = value[0];
src/java.base/share/classes/java/lang/Long.java line 561:
> 559: return parseLong0(s, radix);
> 560: }
> 561: int fc = value[0];
Suggestion:
/* Accumulating negatively avoids surprises near MAX_VALUE */
int fc = value[0];
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/22919#discussion_r1940916020
PR Review Comment: https://git.openjdk.org/jdk/pull/22919#discussion_r1940916196
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