> 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.
Chris Hennick has updated the pull request incrementally with two additional commits since the last revision: - Merge remote-tracking branch 'origin/patch-1' into patch-1 - Optimize: move some code out of the fast path ------------- Changes: - all: https://git.openjdk.org/jdk/pull/8131/files - new: https://git.openjdk.org/jdk/pull/8131/files/2470c00a..e4714ec9 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=8131&range=19 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=8131&range=18-19 Stats: 20 lines in 1 file changed: 10 ins; 10 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/8131.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/8131/head:pull/8131 PR: https://git.openjdk.org/jdk/pull/8131
