RFR: 8341402: BigDecimal's square root optimization [v20]

[Raffaello Giulietti]

On Tue, 19 Nov 2024 19:02:09 GMT, fabioromano1 <duke at openjdk.org> wrote:

>> src/java.base/share/classes/java/math/BigDecimal.java line 2253:
>> 
>>> 2251: 
>>> 2252:                     case UP, CEILING -> {
>>> 2253:                         BigInteger[] sqrtRem = workingInt.sqrtAndRemainder();
>> 
>> Can't this follow the same logic as for the halfway cases, with just `sqrt()` and a `!workingInt.equals(sqrt.multiply(sqrt))` test? This would increase consistency.
>> Are there performance reasons to do it as in the current code?
>
> Yes, indeed in this case the remainder is always needed, so invoking `workingInt.sqrtAndRemainder()` is faster than checking `!workingInt.equals(sqrt.multiply(sqrt))`, as it avoids the squaring of `sqrt`.

I see.

I have no other comments on the code. I look forward for the tests.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21301#discussion_r1848971914