RFR: 8367603: Optimize exact division in BigDecimal [v17]

[Raffaello Giulietti]

On Fri, 26 Sep 2025 07:34:55 GMT, fabioromano1 <duke at openjdk.org> wrote:

>> A formula to lower the overestimate for the precision of an exact quotient, without introducing too expensive operations of division on numerator and denominator.
>
> fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Minor change

I can confirm the substantial speedups.

On macOS 15.7/MacBook Pro/M1 Pro + 32 GiB

before

Benchmark                           Mode  Cnt       Score      Error  Units
BigDecimalDivide.testExactDivideL   avgt   15   64633.600 ± 2371.205  ns/op
BigDecimalDivide.testExactDivideM   avgt   15    7861.471 ±  310.141  ns/op
BigDecimalDivide.testExactDivideS   avgt   15    2255.149 ±   49.171  ns/op
BigDecimalDivide.testExactDivideXL  avgt   15  429182.687 ± 4048.599  ns/op
BigDecimalDivide.testExactDivideXS  avgt   15    1553.006 ±   39.593  ns/op


after

Benchmark                           Mode  Cnt      Score     Error  Units
BigDecimalDivide.testExactDivideL   avgt   15   3348.603 ±  70.500  ns/op
BigDecimalDivide.testExactDivideM   avgt   15   1141.554 ±  23.310  ns/op
BigDecimalDivide.testExactDivideS   avgt   15    877.720 ±  20.571  ns/op
BigDecimalDivide.testExactDivideXL  avgt   15  20038.746 ± 418.701  ns/op
BigDecimalDivide.testExactDivideXS  avgt   15    780.262 ±   5.139  ns/op

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PR Comment: https://git.openjdk.org/jdk/pull/27271#issuecomment-3338607330