> This PR improves both the 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 > greatly reduce the probability that `nextGaussian` suffers from *two* tail > cases of `nextExponential`.
Chris Hennick has updated the pull request incrementally with one additional commit since the last revision: Weaken contract of computeWinsorizedNextExponential to save max/min calls ------------- Changes: - all: https://git.openjdk.org/jdk/pull/8131/files - new: https://git.openjdk.org/jdk/pull/8131/files/cab6b5bb..5919faeb Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=8131&range=11 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=8131&range=10-11 Stats: 17 lines in 1 file changed: 0 ins; 5 del; 12 mod Patch: https://git.openjdk.org/jdk/pull/8131.diff Fetch: git fetch https://git.openjdk.org/jdk pull/8131/head:pull/8131 PR: https://git.openjdk.org/jdk/pull/8131
