RFR: 8334755: Asymptotically faster implementation of square root algorithm [v23]

[fabioromano1]

On Fri, 12 Jul 2024 13:07:02 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Added comment on normalization in MutableBigInteger.sqrtRemZimmermann()
>
> src/java.base/share/classes/java/math/MutableBigInteger.java line 1997:
> 
>> 1995:         if (len == 2) { // Base case
>> 1996:             long x = ((value[offset] & LONG_MASK) << 32) | (value[offset + 1] & LONG_MASK);
>> 1997:             long s = (long) Math.sqrt(x > 0 ? x : x + 0x1p64);
> 
> Again, this needs a proof that doing so is always correct.
> 
> Suggestion:
> 
>             long s = (long) Math.sqrt(x >= 0 ? x : x + 0x1p64);

Here there's no need to modify `x > 0` with `x >= 0`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19710#discussion_r1675972896