RFR 8222955 : Optimize String.replace(CharSequence, CharSequence) for Latin1 encoded strings

[Ivan Gerasimov]

Hi Sergei!

Thanks for sharing.

However, it's not immediately obvious to me why the later is better than 
the former.  Can you please elaborate on that?

I think, it worth a separate discussion.

With kind regards,

Ivan


On 4/25/19 12:40 AM, Сергей Цыпанов wrote:
> Hi Ivan,
>
> recently looking into java.lang.String I've found out that String::split still uses old collection-to-array approach:
>
> String[] result = new String[resultSize];
> return list.subList(0, resultSize).toArray(result);
>
> which should be replaced with
>
> return list.subList(0, resultSize).toArray(new String[0]);
>
> this changes is too small to create a separate ticket for this, so could I ask you to add this into your changes?
>
> Regards,
> Sergei Tsypanov
>
>
> 25.04.2019, 08:04, "Ivan Gerasimov" <ivan.gerasimov at oracle.com>:
>> Hello!
>>
>> This enhancement was inspired by a recent discussion at
>> compiler-dev at openjdk.java.net.
>>
>> It seems to be a non-uncommon situation when String.replace(CS, CS) is
>> called with this and both arguments being Latin1 strings, so it seems
>> reasonable to optimize for such case.
>>
>> Here are the fresh benchmark results (see the webrev for the source of
>> the benchmark):
>> -- prior the fix:
>> Benchmark Mode Cnt Score Error Units
>> StringReplace.replace1_0 avgt 24 70.860 ± 5.239 ns/op
>> StringReplace.replace1_1 avgt 24 82.661 ± 1.007 ns/op
>> StringReplace.replace1_2 avgt 24 97.251 ± 1.186 ns/op
>>
>> -- after the fix:
>> Benchmark Mode Cnt Score Error Units
>> StringReplace.replace1_0 avgt 24 52.855 ± 0.982 ns/op
>> StringReplace.replace1_1 avgt 24 23.849 ± 0.066 ns/op
>> StringReplace.replace1_2 avgt 24 62.266 ± 0.552 ns/op
>>
>> So the speedup was x1.3, x3.4, x1.5.
>>
>> Would you please help review the fix?
>>
>> BUGURL: https://bugs.openjdk.java.net/browse/JDK-8222955
>> WEBREV: http://cr.openjdk.java.net/~igerasim/8222955/00/webrev/
>>
>> Mach5 job is in progress and looks green so far (a few test groups are
>> left).
>>
>> Thanks in advance!
>>
>> --
>> With kind regards,
>> Ivan Gerasimov

-- 
With kind regards,
Ivan Gerasimov