RFR: 8341402: BigDecimal's square root optimization

[Raffaello Giulietti]

On Wed, 2 Oct 2024 10:31:09 GMT, fabioromano1 <duke at openjdk.org> wrote:

> After changing `BigInteger.sqrt()` algorithm, this can be also used to speed up `BigDecimal.sqrt()` implementation. Here is how I made it.
> 
> The main steps of the algorithm are as follows:
> first argument reduce the value to an integer using the following relations:
> 
> x = y * 10 ^ exp
> sqrt(x) = sqrt(y) * 10^(exp / 2) if exp is even
> sqrt(x) = sqrt(y*10) * 10^((exp-1)/2) is exp is odd
> 
> Then use BigInteger.sqrt() on the reduced value to compute the numerical digits of the desired result.
> 
> Finally, scale back to the desired exponent range and perform any adjustment to get the preferred scale in the representation.

Looking at the code, the divisors are quite limited, so my hypothesis above and the suggestions are out of place.

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PR Comment: https://git.openjdk.org/jdk/pull/21301#issuecomment-2388696062