On 05/07/2015 03:58 PM, Luc Maisonobe wrote: > Le 07/05/2015 15:42, Thomas Neidhart a écrit : >> I did not want to invalidate your effort, > > > Don't worry about that. I learned a lot doing this, including > something that really surprised me: pow(NaN, 0.0) *must* be 1.0 > and not NaN. AFAIK this is the only case where a NaN input does not > propagate to output. > > >> but check if a faulty branch >> prediction / optimization might be the cause of the problem, which seems to >> be confirmed now. > > Yes, it seems to be the problem. > >> >> If you have an improved version of the pow function, please go ahead with >> your modifications. > > It doesn't improve anything, I run the performance benchmark and the > results are exactly the same as our previous implementation, neither > faster nor slower. > > Could you merge your change back to master?
ok, merged. I first read some something related to JIT branch optimization in this article: http://www.javacodegeeks.com/2013/06/jvm-performance-magic-tricks.html The example there is quite scary imho but I am not sure if this is really happening or allowed for the JIT compiler to do. Maybe in our case it is simply a bug that occurs also only on very specific hardware. Thomas --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
