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Date: Tue, 14 Aug 2012 14:39:29 -0500
From: Stephen Montgomery-Smith <stephen@missouri.edu>
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Cc: freebsd-numerics@freebsd.org
Subject: Re: Status of expl logl
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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