RFR: 8077587: BigInteger Roots [v78]

[Raffaello Giulietti]

On Fri, 29 Aug 2025 19:00:23 GMT, fabioromano1 <duke at openjdk.org> wrote:

>> This PR implements nth root computation for BigIntegers using Newton method.
>
> fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revision changes

I think the PR is in a good state.

src/java.base/share/classes/java/math/MutableBigInteger.java line 2040:

> 2038:                 } else {
> 2039:                     // Discard wrong integer bits from the initial estimate
> 2040:                     // The radicand has Math.getExponent(rad)+1 integer bits, but only

Suggestion:

                    // The reduced radicand rad has Math.getExponent(rad)+1 integer bits, but only

src/java.base/share/classes/java/math/MutableBigInteger.java line 2059:

> 2057:                 /* The Newton's recurrence roughly duplicates the correct bits at each iteration.
> 2058:                  * Instead of shifting the approximate root into the original range right now,
> 2059:                  * we only duplicate its bit length and then refine it with Newton's recurrence,

Suggestion:

                /* The Newton's recurrence roughly doubles the correct bits at each iteration.
                 * Instead of shifting the approximate root into the original range right now,
                 * we only double its bit length and then refine it with Newton's recurrence,

src/java.base/share/classes/java/math/MutableBigInteger.java line 2060:

> 2058:                  * Instead of shifting the approximate root into the original range right now,
> 2059:                  * we only duplicate its bit length and then refine it with Newton's recurrence,
> 2060:                  * using a congruent shifted radicand, in order to avoid computing and

Maybe clarify what "congruent" means here

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PR Review: https://git.openjdk.org/jdk/pull/24898#pullrequestreview-3179775832
PR Review Comment: https://git.openjdk.org/jdk/pull/24898#discussion_r2318360217
PR Review Comment: https://git.openjdk.org/jdk/pull/24898#discussion_r2318360557
PR Review Comment: https://git.openjdk.org/jdk/pull/24898#discussion_r2318360386