RFR: 8316704: Regex-free parsing of Formatter and FormatProcessor specifiers

[Shaojin Wen]

On Thu, 28 Sep 2023 15:01:25 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> @cl4es made performance optimizations for the simple specifiers of String.format in PR https://github.com/openjdk/jdk/pull/2830. Based on the same idea, I continued to make improvements. I made patterns like %2d %02d also be optimized.
>> 
>> The following are the test results based on MacBookPro M1 Pro: 
>> 
>> 
>> -Benchmark                          Mode  Cnt     Score     Error  Units
>> -StringFormat.complexFormat         avgt   15  1862.233 ? 217.479  ns/op
>> -StringFormat.int02Format           avgt   15   312.491 ?  26.021  ns/op
>> -StringFormat.intFormat             avgt   15    84.432 ?   4.145  ns/op
>> -StringFormat.longFormat            avgt   15    87.330 ?   6.111  ns/op
>> -StringFormat.stringFormat          avgt   15    63.985 ?  11.366  ns/op
>> -StringFormat.stringIntFormat       avgt   15    87.422 ?   0.147  ns/op
>> -StringFormat.widthStringFormat     avgt   15   250.740 ?  32.639  ns/op
>> -StringFormat.widthStringIntFormat  avgt   15   312.474 ?  16.309  ns/op
>> 
>> +Benchmark                          Mode  Cnt    Score    Error  Units
>> +StringFormat.complexFormat         avgt   15  740.626 ? 66.671  ns/op (+151.45)
>> +StringFormat.int02Format           avgt   15  131.049 ?  0.432  ns/op (+138.46)
>> +StringFormat.intFormat             avgt   15   67.229 ?  4.155  ns/op (+25.59)
>> +StringFormat.longFormat            avgt   15   66.444 ?  0.614  ns/op (+31.44)
>> +StringFormat.stringFormat          avgt   15   62.619 ?  4.652  ns/op (+2.19)
>> +StringFormat.stringIntFormat       avgt   15   89.606 ? 13.966  ns/op (-2.44)
>> +StringFormat.widthStringFormat     avgt   15   52.462 ? 15.649  ns/op (+377.95)
>> +StringFormat.widthStringIntFormat  avgt   15  101.814 ?  3.147  ns/op (+206.91)
>
> Meaningful external reviews take a _lot_ of engineering time on such a popular platform as the JDK.
> They make sense only on somehow stable code, otherwise they are a waste of human resources.
> 
> So sure, take your time to stabilize your code, make your tests, but please refrain from keep on changing too much once you publish a PR. If reviewers have to face continuous changes, they might become uninterested in reviewing.

Thanks to @rgiulietti for the review, I have changed the FormatProcessor according to your suggestion and added test cases

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PR Comment: https://git.openjdk.org/jdk/pull/15776#issuecomment-1770659922