Date: Sun, 29 Jul 2012 17:39:27 -0500 From: Stephen Montgomery-Smith <stephen@missouri.edu> To: freebsd-numerics@FreeBSD.org Cc: Diane Bruce <db@db.net>, Bruce Evans <brde@optusnet.com.au>, John Baldwin <jhb@FreeBSD.org>, David Chisnall <theraven@FreeBSD.org>, Bruce Evans <bde@FreeBSD.org>, Steve Kargl <sgk@troutmask.apl.washington.edu>, David Schultz <das@FreeBSD.org>, Peter Jeremy <peter@rulingia.com>, Warner Losh <imp@bsdimp.com> Subject: Re: Use of C99 extra long double math functions after r236148 Message-ID: <5015BB9F.90807@missouri.edu> In-Reply-To: <20120729222706.GA29048@server.rulingia.com> References: <20120718123627.D1575@besplex.bde.org> <20120722121219.GC73662@server.rulingia.com> <500DAD41.5030104@missouri.edu> <20120724113214.G934@besplex.bde.org> <501204AD.30605@missouri.edu> <20120727032611.GB25690@server.rulingia.com> <20120728125824.GA26553@server.rulingia.com> <501460BB.30806@missouri.edu> <20120728231300.GA20741@server.rulingia.com> <50148F02.4020104@missouri.edu> <20120729222706.GA29048@server.rulingia.com>
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On 07/29/2012 05:27 PM, Peter Jeremy wrote: > [For anyone not previously in on this discussion, this is part of an > ongoing discussion that has been occurring off-list in the absence of > a suitable list. It is planned to archive that discussion here, > subject to all the participants agreeing]. > > On 2012-Jul-28 20:16:50 -0500, Stephen Montgomery-Smith <stephen@missouri.edu> wrote: >> One thing your program doesn't check are things like: >> >> real part of casinh(-0+I*x) is -0 >> imaginary part of casinh(x-I*0) is -0 >> >> etc, where x is finite, non-zero. (This follows from casinh being odd >> and conjugate invariant.) > > As it currently exists, my program solely implements the checks in > WG14/N1256 G.6. I hadn't considered extending that to verifying that > purely real or imaginary inputs give purely real or imaginary outputs, > with the appropriately signed zero. This might be reasonable but it's > not completely trivial to implement in general since the domains of > the real part can be different. Maybe this should be a different program, since its logical structure would be quite different. In particular, you wouldn't be checking the value of the non-zero parts. Also I forgot that the real part of casinh(0+I*x) isn't always 0. If |x|>1, it is something non-zero. And so you need to check that creal(casinh(0+I*x)) and creal(casinh(-0+I*x)) have opposite signs in this case. > I'm less sure of the next logical > step, which is to check things like > casinh(x + I*0) = asinh(x) + I*0 Does C99 mandate this? My programs probably won't satisfy this, because I realized that the computation works in these cases anyway. Of course, it would be easy to make it happen.
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