On Wed, 6 Apr 2022 17:47:53 GMT, Chris Hennick <d...@openjdk.org> wrote:
> This PR improves both the worst-case performance of `nextExponential` and > `nextGaussian` and the distribution of output at the tails. It fixes the > following imperfections: > > * Repeatedly adding DoubleZigguratTables.exponentialX0 to extra causes a > rounding error to accumulate at the tail of the distribution (probably > starting around `2*exponentialX0 == 0x1.e46eff20739afp3 ~ 15.1`); this PR > fixes that by tracking the multiple of exponentialX0 as a long. (This > distortion is worst when `x > 0x1.0p56` since in that case, a rounding error > means `extra + x == extra`. > * Reduces several equations using `Math.fma`. (This will almost certainly > improve performance, and may or may not improve output distribution.) > * Uses the newly-extracted `computeWinsorizedNextExponential` function to > prevent `nextGaussian` from going into the `nextExponential` tail twice. This pull request has now been integrated. Changeset: f975be44 Author: Chris Hennick <4961925+pr0meth...@users.noreply.github.com> Committer: Joe Darcy <da...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/f975be44a86879e1079a0066203b49d59b7a1167 Stats: 144 lines in 4 files changed: 128 ins; 0 del; 16 mod 8284493: Improve computeNextExponential tail performance and accuracy Reviewed-by: darcy ------------- PR: https://git.openjdk.org/jdk/pull/8131
