RFR: 8341470: BigDecimal.stripTrailingZeros() optimization [v12]

[Archie Cobbs]

On Thu, 3 Oct 2024 17:11:09 GMT, fabioromano1 <duke at openjdk.org> wrote:

>> An optimized algorithm for `BigDecimal.stripTrailingZeros()` that uses repeated squares trick.
>
> fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Code simplification

src/java.base/share/classes/java/math/BigDecimal.java line 5238:

> 5236:             BigInteger pow = FIVE_TO_2_TO[FIVE_TO_2_TO_LEN - 1];
> 5237:             for (int i = FIVE_TO_2_TO_LEN; i <= n; i++)
> 5238:                 FIVE_TO_2_TO[i] = pow = pow.multiply(pow);

Drive-by comment... apologies if I'm missing some subtle context. Doesn't this raciness create a bug? The field `FIVE_TO_2_TO_LEN` is read multiple times, and other threads could be incrementing it while this code executes, which would lead to an incorrect value for `pow`, etc.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21323#discussion_r1786580894