On Tue, 25 May 2021 15:32:40 GMT, gregcawthorne <d...@openjdk.java.net> wrote:
>> Glibc 2.29 onwards provides optimised versions of log,log10,exp. >> These functions have an accuracy of 0.9ulp or better in glibc >> 2.29. >> >> Therefore this patch adds code to parse, store and check >> the runtime glibcs version in os_linux.cpp/hpp. >> This is then used to select the glibcs implementation of >> log, log10, exp at runtime for c1 and c2, iff we have >> glibc 2.29 or greater. >> >> This will ensure OpenJDK can benefit from future improvements >> to glibc. >> >> Glibc adheres to the ieee754 standard, unless stated otherwise >> in its spec. >> >> As there are no stated exceptions in the current glibc spec >> for dlog, dlog10 and dexp, we can assume they currently follow >> ieee754 (which testing confirms). As such, future version of >> glibc are unlikely to lose this compliance with ieee754 in >> future. >> >> W.r.t performance this patch sees ~15-30% performance improvements for >> log and log10, with ~50-80% performance improvements for exp for the >> common input ranged (which output real numbers). However for the NaN >> and inf output ranges we see a slow down of up to a factor of 2 for >> some functions and architectures. >> >> Due to this being the uncommon case we assert that this is a >> worthwhile tradeoff. > > greg.cawtho...@arm.com > > Should work @gregcawthorne any plans to re-open and fix this? ------------- PR: https://git.openjdk.java.net/jdk/pull/3510
