RFR: 8366478: BigDecimal roots [v4]

[Raffaello Giulietti]

On Wed, 15 Oct 2025 15:56:46 GMT, fabioromano1 <duke at openjdk.org> wrote:

>> An implementation of `BigDecimal.nthRoot(int, MathContext)`.
>
> fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Comment for error analysis

src/java.base/share/classes/java/math/BigDecimal.java line 2160:

> 2158:      *
> 2159:      * <p>The preferred scale of the returned result is equal to
> 2160:      * {@code this.scale()/n}. The value of the returned result is

I think the preferred scale should be ceiling(this.scale() / n).
The IEEE 754 standard has a preferred exponent (negated scale) of floor(exp(this) / n).

src/java.base/share/classes/java/math/BigDecimal.java line 2181:

> 2179:      * @param mc the context to use.
> 2180:      * @return the {@code n}<sup>th</sup> root of {@code this}.
> 2181:      * @throws ArithmeticException if {@code n == 0 || n == Integer.MIN_VALUE}.

Just out of curiosity, is there a technical reason for the restriction on MIN_VALUE?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27148#discussion_r2436648335
PR Review Comment: https://git.openjdk.org/jdk/pull/27148#discussion_r2436648498