On Fri, 4 Oct 2024 16:09:28 GMT, Shaojin Wen <s...@openjdk.org> wrote:
>> fabioromano1 has updated the pull request incrementally with two additional >> commits since the last revision: >> >> - Merge branch 'patchStripTrailingZeros' of >> https://github.com/fabioromano1/jdk into patchStripTrailingZeros >> - Added benchmark tests > > Expand the length of FIVE_TO_2_TO to 32 and use `& 0x1F` when accessing the > array to eliminate bounds checks. > > private static final BigInteger[] FIVE_TO_2_TO = new BigInteger[32]; // 30 > -> 32 > > > private static BigInteger fiveToTwoToThe(int n) { > if (n >= FIVE_TO_2_TO_LEN) { > BigInteger pow = FIVE_TO_2_TO[(FIVE_TO_2_TO_LEN - 1) & 0x1F]; // > & 0x1F eliminate bounds checks. > for (int i = FIVE_TO_2_TO_LEN; i <= n; i++) > FIVE_TO_2_TO[i & 0x1F] = pow = pow.multiply(pow); // & 0x1F > eliminate bounds checks. > > FIVE_TO_2_TO_LEN = n + 1; > } > > return FIVE_TO_2_TO[n & 0x1F]; // & 0x1F eliminate bounds checks. > } @wenshao I don't think it makes any practical difference in performance, and the code becomes a bit more convoluted. The need for comments to enlighten the reader is suspicious. These tricks are great in time critical code, but IMO this is not the case here. ------------- PR Comment: https://git.openjdk.org/jdk/pull/21323#issuecomment-2394076573
