[PATCH] Trivial improvement for j.l.Character.toString() - 8241649: Optimize Character.toString

[Claes Redestad]

Good catch. Closed it as duplicate - also surprised myself that I didn't
find this one when I did a cursory search in JBS for pre-existing
issues.

/Claes

On 2020-04-06 07:24, Anirvan Sarkar wrote:
> JDK-8189375 <https://bugs.openjdk.java.net/browse/JDK-8189375> should be 
> closed as duplicate.
> 
> On Thu, 26 Mar 2020 at 18:06, Claes Redestad <claes.redestad at oracle.com 
> <mailto:claes.redestad at oracle.com>> wrote:
> 
>     Filed and pushed: https://bugs.openjdk.java.net/browse/JDK-8241649
> 
>     /Claes
> 
>     On 2020-03-26 00:12, Roger Riggs wrote:
>      > Agreed,  +1
>      >
>      > On 3/25/20 5:53 PM, Claes Redestad wrote:
>      >> Looks good and trivial, including the drive-by cleanups.
>      >>
>      >> I can sponsor.
>      >>
>      >> /Claes
>      >>
>      >> On 2020-03-25 22:18, Сергей Цыпанов wrote:
>      >>> Hello,
>      >>>
>      >>> I think we can reduce allocation rate for
>     j.l.Character.toString() by
>      >>> calling String.valueOf(char) instead of String.valueOf(char[]).
>      >>>
>      >>> Current implementation creates char[] with one char which is later
>      >>> decoded into byte[].
>      >>>
>      >>> Instead String.valueOf(char) decodes char directly consuming less
>      >>> memory. I've used benchmark [1]
>      >>> and on my machine got those results (JDK 14):
>      >>>
>      >>> Benchmark Mode    Score     Error   Units
>      >>>
>      >>> CharacterToStringBenchmark.toString_utf8 avgt   14.723 ±  
>     1.354   ns/op
>      >>> CharacterToStringBenchmark.valueOf_utf8 avgt    7.678 ±  
>     0.601   ns/op
>      >>>
>      >>> CharacterToStringBenchmark.toString_latin avgt   10.992 ±  
>     1.371 ns/op
>      >>> CharacterToStringBenchmark.valueOf_latin avgt    7.844 ±  
>     1.044   ns/op
>      >>>
>      >>> CharacterToStringBenchmark.toString_utf8:·gc.alloc.rate.norm avgt
>      >>> 96.003 ±   0.001    B/op
>      >>> CharacterToStringBenchmark.valueOf_utf8:·gc.alloc.rate.norm avgt
>      >>> 48.002 ±   0.001    B/op
>      >>>
>      >>> CharacterToStringBenchmark.toString_latin:·gc.alloc.rate.norm avgt
>      >>> 72.003 ±   0.001    B/op
>      >>> CharacterToStringBenchmark.valueOf_latin:·gc.alloc.rate.norm avgt
>      >>> 48.002 ±   0.001    B/op
>      >>>
>      >>>
>      >>> Patch is below.
>      >>>
>      >>> With best regards,
>      >>> Sergey Tsypanov
>      >>>
>      >>> [1]
>      >>>
>     https://github.com/stsypanov/strings/blob/master/src/jmh/java/tsypanov/strings/character/CharacterToStringBenchmark.java
> 
>      >>>
>      >>>
>      >>> diff --git a/src/java.base/share/classes/java/lang/Character.java
>      >>> b/src/java.base/share/classes/java/lang/Character.java
>      >>> --- a/src/java.base/share/classes/java/lang/Character.java
>      >>> +++ b/src/java.base/share/classes/java/lang/Character.java
>      >>> @@ -3285,7 +3285,7 @@
>      >>>                                "SYMBOLS AND PICTOGRAPHS
>     EXTENDED-A",
>      >>> "SYMBOLSANDPICTOGRAPHSEXTENDED-A");
>      >>>   -        private static final int blockStarts[] = {
>      >>> +        private static final int[] blockStarts = {
>      >>>               0x0000,   // 0000..007F; Basic Latin
>      >>>               0x0080,   // 0080..00FF; Latin-1 Supplement
>      >>>               0x0100,   // 0100..017F; Latin Extended-A
>      >>> @@ -8068,7 +8068,7 @@
>      >>>               UNKNOWN,                  // E01F0..10FFFF
>      >>>           };
>      >>>   -        private static HashMap<String, Character.UnicodeScript>
>      >>> aliases;
>      >>> +        private static final HashMap<String,
>      >>> Character.UnicodeScript> aliases;
>      >>>           static {
>      >>>               aliases = new HashMap<>((int)(153 / 0.75f + 1.0f));
>      >>>               aliases.put("ADLM", ADLAM);
>      >>> @@ -8421,8 +8421,7 @@
>      >>>        * @return  a string representation of this object.
>      >>>        */
>      >>>       public String toString() {
>      >>> -        char buf[] = {value};
>      >>> -        return String.valueOf(buf);
>      >>> +        return toString(value);
>      >>>       }
>      >>>         /**
>      >>>
>      >
> 
> 
> 
> -- 
> Anirvan