On Fri, 25 Jul 2025 15:24:22 GMT, fabioromano1 <d...@openjdk.org> wrote:
>> src/java.base/share/classes/java/math/MutableBigInteger.java line 1967: >> >>> 1965: sToN1 = BigInteger.unsignedLongPow(sLong, n - 1); >>> 1966: u = ((n - 1) * sLong + Long.divideUnsigned(x, >>> sToN1)) / n; >>> 1967: } while (u < sLong); // Terminate when non-decreasing. >> >> I'm not sure this is 100% correct. >> Since one "iteration" is done before even entering the loop, I think the >> loop condition should go to the beginning. >> As it is now, there are always two evaluations of the Newton recurrence >> formula. > > No, the loop condition should not go to the beginning, because the 1st > iteration is not related with the loop, but it serves to satisfy the > precondition that guarantees the correctness after the termination of the > loop. Indeed, the loop condition can't be evaluated after the first > iteration, because `u` is not defined yet. If it were, doing the 1st > iteration in the loop would make no difference, but the loop could stop with > a wrong value of `s`. > As it is now, there are always two evaluations of the Newton recurrence > formula. In other words, two evaluations of the Newton recurrence are always needed. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/24898#discussion_r2231438424
