RFR: 8341402: BigDecimal's square root optimization [v2]

[fabioromano1]

On Wed, 2 Oct 2024 18:16:06 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> A possible faster implementation of `stripZerosToMatchScale()` could be based on dividing by increasing powers of 10 whose exponent doubles at each step (a kind of repeated squares trick), although the asymptotic running time would still be exponential.
>
> Without experimenting a bit, it's hard to tell.
> Anyway, I believe the current implementation of `stripZerosToMatchScale()` is O(n^2) rather than exponential, because each single division by 10 is linear.
> 
> But let's focus on `sqrt()` in this PR and leave `stripZerosToMatchScale()` for another time.

@rgiulietti  I tried to implement and test stripping zeros  algorithm with repeated squares trick, and on my laptop it takes around two seconds for strip one million of zeros. So, I decided to remove the method `stripZerosToEvenScale()`, in order to use only the `stripZerosToMatchScale()` logic.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21301#discussion_r1785790063