Date: Sun, 12 Aug 2012 23:05:19 -0000 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Warner Losh <imp@bsdimp.com> Cc: Diane Bruce <db@db.net>, John Baldwin <jhb@freebsd.org>, David Chisnall <theraven@freebsd.org>, Stephen Montgomery-Smith <stephen@missouri.edu>, Bruce Evans <bde@freebsd.org>, Bruce Evans <brde@optusnet.com.au>, David Schultz <das@freebsd.org>, Peter Jeremy <peter@rulingia.com> Subject: Re: Use of C99 extra long double math functions after r236148 Message-ID: <20120717042434.GA87001@troutmask.apl.washington.edu> Resent-Message-ID: <20120812230511.GS20453@server.rulingia.com> In-Reply-To: <6F750F84-34FF-4961-A2EA-F3E67A6872AE@bsdimp.com> References: <201207130818.38535.jhb@freebsd.org> <9EB2DA4F-19D7-4BA5-8811-D9451CB1D907@theravensnest.org> <C527B388-3537-406F-BA6D-2FA45B9EAA3B@FreeBSD.org> <20120713155805.GC81965@zim.MIT.EDU> <20120714120432.GA70706@server.rulingia.com> <20120717084457.U3890@besplex.bde.org> <5004A5C7.1040405@missouri.edu> <5004DEA9.1050001@missouri.edu> <20120717040118.GA86840@troutmask.apl.washington.edu> <6F750F84-34FF-4961-A2EA-F3E67A6872AE@bsdimp.com>
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On Mon, Jul 16, 2012 at 10:12:21PM -0600, Warner Losh wrote: > > On Jul 16, 2012, at 10:01 PM, Steve Kargl wrote: > > > On Mon, Jul 16, 2012 at 10:40:25PM -0500, Stephen Montgomery-Smith wrote: > >> > >> I came up with pseudo code that looks a bit like this. > >> > >> complex casinh(complex z) { > >> double x = z.re, y = z.im; > >> > >> if (y==0) > >> return asinh(x); > >> if (x==0) { > >> if (fabs(y)<=1) return I*asin(y); > >> else return signum(y)* ( > >> log(fabs(y)+sqrt(y*y-1)) > >> + I*PI/2); > > > > Stop. Please see msun/src/math_private.h. You cannot > > use I in any expression. gcc in base and clang do not > > do the arithmetic correctly. See msun/src/s_ccosh.c > > for how one might approach writing these functions. > > Also, consult n1256.pdf for x,y = +-0, +-inf, nan. > > There are specific requirements that must be met. > > Yes. Pseudo code is OK for following the flow, but look at the > exp code for why that's not entirely sufficient. You have to be > extremely fussy about all kinds of things. Then again, exp is a > lot more important to get right than the complex trig functions... > > The pseudo code is a good place to start, but it just the barest > start in the integration process... I can't tell whether you agree with my urging of caution or whether your being sarcastic. The pseudo-code as written simply does not apply once one looks at n1256.pdf. -- Steve
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