RFR: 8310929: Optimization for Integer.toString [v2]

[温绍锦]

On Wed, 28 Jun 2023 22:19:04 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> Speed up Integer.toString with a precomputed cache array of length 1000, use division by 1000, so that each iteration can calculate three digits.  
>> 
>> this optimization can also be used in StringBuilder#appent(int) and Long#toString.
>> 
>> # Benchmark Result
>> 
>> 
>> bash configure --with-jmh=build/jmh/jars
>> make test TEST="micro:java.lang.Integers.toString*"
>> 
>> 
>> ## 1. [aliyun_ecs_c8i.xlarge](https://help.aliyun.com/document_detail/25378.html#c8i)
>> * cpu : intel xeon sapphire rapids (x64)
>> ``` diff
>> -Benchmark               (size)  Mode  Cnt  Score   Error  Units (baseline)
>> -Integers.toStringBig       500  avgt   15  6.811 ± 0.016  us/op
>> -Integers.toStringSmall     500  avgt   15  4.794 ± 0.011  us/op
>> -Integers.toStringTiny      500  avgt   15  3.752 ± 0.065  us/op
>> 
>> +Benchmark               (size)  Mode  Cnt  Score   Error  Units (PR commit-id 3355d211)
>> +Integers.toStringBig       500  avgt   15  5.148 ± 0.044  us/op (+32.30%)
>> +Integers.toStringSmall     500  avgt   15  3.820 ± 0.016  us/op (+25.48%)
>> +Integers.toStringTiny      500  avgt   15  3.426 ± 0.010  us/op (+9.51%)
>> 
>> 
>> ## 2. [aliyun_ecs_c8a.xlarge](https://help.aliyun.com/document_detail/25378.html#c8a)
>> * cpu : amd epc genoa (x64)
>> ``` diff
>> -Benchmark               (size)  Mode  Cnt  Score   Error  Units (baseline)
>> -Integers.toStringBig       500  avgt   15  6.762 ± 0.018  us/op
>> -Integers.toStringSmall     500  avgt   15  4.481 ± 0.004  us/op
>> -Integers.toStringTiny      500  avgt   15  2.761 ± 0.012  us/op
>> 
>> +Benchmark               (size)  Mode  Cnt  Score   Error  Units (PR commit-id 3355d211)
>> +Integers.toStringBig       500  avgt   15  4.901 ± 0.005  us/op (+37.97%)
>> +Integers.toStringSmall     500  avgt   15  3.515 ± 0.204  us/op (+27.48%)
>> +Integers.toStringTiny      500  avgt   15  2.698 ± 0.190  us/op (+2.33%)
>> 
>> 
>> ## 3. [aliyun_ecs_c8y.xlarge](https://help.aliyun.com/document_detail/25378.html#c8y)
>> * cpu : aliyun yitian 710 (aarch64)
>> ``` diff
>> -Benchmark               (size)  Mode  Cnt   Score   Error  Units (baseline)
>> -Integers.toStringBig       500  avgt   15  12.081 ± 0.377  us/op
>> -Integers.toStringSmall     500  avgt   15   7.119 ± 0.177  us/op
>> -Integers.toStringTiny      500  avgt   15   6.323 ± 0.239  us/op
>> 
>> +Benchmark               (size)  Mode  Cnt  Score   Error  Units (PR commit-id 3355d211)
>> +Integers.toStringBig       500  avgt   15  8.279 ± 0.184  us/op (+45.92%)
>> +Integers.toStringSmall     500  avgt   15  7.2...
>
> 温绍锦 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   postpone the division

> ```diff
> 9.51
> ```

caching tinyInt result string is a good idea, it can improve performance, but it is expensive, i am not sure whether it should be added.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/14699#issuecomment-1613582797