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Date:      Fri, 21 Sep 2012 21:34:18 +1000 (EST)
From:      Bruce Evans <brde@optusnet.com.au>
To:        Bruce Evans <brde@optusnet.com.au>
Cc:        Stephen Montgomery-Smith <stephen@missouri.edu>, freebsd-numerics@FreeBSD.org
Subject:   Re: Complex arg-trig functions
Message-ID:  <20120921212525.W1732@besplex.bde.org>
In-Reply-To: <20120921172402.W945@besplex.bde.org>
References:  <5017111E.6060003@missouri.edu> <5051F59C.6000603@missouri.edu> <20120914014208.I2862@besplex.bde.org> <50526050.2070303@missouri.edu> <20120914212403.H1983@besplex.bde.org> <50538E28.6050400@missouri.edu> <20120915231032.C2669@besplex.bde.org> <50548E15.3010405@missouri.edu> <5054C027.2040008@missouri.edu> <5054C200.7090307@missouri.edu> <20120916041132.D6344@besplex.bde.org> <50553424.2080902@missouri.edu> <20120916134730.Y957@besplex.bde.org> <5055ECA8.2080008@missouri.edu> <20120917022614.R2943@besplex.bde.org> <50562213.9020400@missouri.edu> <20120917060116.G3825@besplex.bde.org> <50563C57.60806@missouri.edu> <20120918012459.V5094@besplex.bde.org> <5057A932.3000603@missouri.edu> <5057F24B.7020605@missouri.edu> <20120918162105.U991@besplex.bde.org> <20120918232850.N2144@besplex.bde.org> <20120919010613.T2493@besplex.bde.org> <505BD9B4.8020801@missouri.edu> <20120921172402.W945@besplex.bde.org>

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On Fri, 21 Sep 2012, I wrote:

> On Thu, 20 Sep 2012, Stephen Montgomery-Smith wrote:
>
>> I also added inexact optimizations for casinh and cacos.
>
> I couldn't get this to give the hoped-for optimization and dropped
> it even for catanh.  You may still prefer it because it is simpler.

It is giving the hoped-for optimizations now...

> But later I found intricacies for returning the correct value of
> Pi/2 which make the inexact optimizations even less useful:

... for the real parts of cacosf(), casin*f(), but not for the real
part of cacoshf().  I tested mainly the latter and catanhf() before,
and the change is still giving a small pessimization for cacoshf().
(I haven't tested the new version for catanhf() yet, and won't test
in so much detail in other precisions).  I think this is because for
cacosh*() alone, inexact is set in more cases while calculating Pi/2.

Bruce



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