RFR: 8341470: BigDecimal.stripTrailingZeros() optimization [v42]

[fabioromano1]

On Sun, 13 Oct 2024 16:06:34 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> What's really crucial for _correctness_ is to ensure maxPowsOf5 >= k.
>> 
>> But for performance you also want maxPowsOf5 to be as small as possible. So, the fact that it turns out that maxPowsOf5 <= m + 1 guarantees that maxPowsOf5 is the best value that can be computed very efficiently. It's more a "quality of service" guarantee than anything fundamental.
>
> Perhaps leave m <= maxPowsOf5 <= m + 1 and maxPowsOf5 >= k and drop the note "and is never off by more than 1 from the theoretical m"

> What's really crucial for _correctness_ is to ensure maxPowsOf5 >= k.

Yes, I meant that the only way we know to ensure that condition is to ensure `m <= maxPowsOf5`...

> Perhaps leave m <= maxPowsOf5 <= m + 1 and maxPowsOf5 >= k and drop the note "and is never off by more than 1 from the theoretical m"

I would put `maxPowsOf5 <= m + 2` instead, because `maxPowsOf5 <= m + 1` is not obvious to prove mathematically...

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PR Review Comment: https://git.openjdk.org/jdk/pull/21323#discussion_r1798437787