Date: Tue, 14 Aug 2012 14:39:29 -0500 From: Stephen Montgomery-Smith <stephen@missouri.edu> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: freebsd-numerics@freebsd.org Subject: Re: Status of expl logl Message-ID: <502AA971.4010403@missouri.edu> In-Reply-To: <20120814183518.GA70092@troutmask.apl.washington.edu> References: <502A8CCC.5080606@missouri.edu> <20120814175257.GA69865@troutmask.apl.washington.edu> <20120814183518.GA70092@troutmask.apl.washington.edu>
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On 08/14/2012 01:35 PM, Steve Kargl wrote: > On Tue, Aug 14, 2012 at 10:52:57AM -0700, Steve Kargl wrote: >> On Tue, Aug 14, 2012 at 12:37:16PM -0500, Stephen Montgomery-Smith wrote: >>> Are people working on expl, logl and log1pl? >>> >> > > I forgot to mention that if you're looking for another > function to implement, then AFAIK no one is working on > ld80/powl() and ld128/powl(). See the comment in > src/e_pow.c for the algorithm used in fdlibm. > So I am looking through src/e_pow.c. It seems to me that the constants L1, L2, L3, etc, are 3/5, 3/7, 3/9, etc, but not exactly these constants. So they must have used some process where they jiggled the constants around, perhaps using trial and error, to get a few extra ulp. Is that right? Also, I am trying to see what P1, P2, P3, etc are. They seem to be related to the factorial (maybe a power series related to exp(x)), but I must admit that I am not getting it. Is there a more detailed reference to how these numbers were obtained? A paper somewhere? Finally, what is ovfl (in the definition of ovt) meant to be? Thanks, Stephen
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