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Date:      Thu, 13 Sep 2012 22:48:51 -0500
From:      Stephen Montgomery-Smith <stephen@missouri.edu>
To:        Bruce Evans <brde@optusnet.com.au>
Cc:        freebsd-numerics@FreeBSD.org
Subject:   cexp error
Message-ID:  <5052A923.9030806@missouri.edu>
In-Reply-To: <20120913204808.T1964@besplex.bde.org>
References:  <5017111E.6060003@missouri.edu> <501D51D7.1020101@missouri.edu> <20120805030609.R3101@besplex.bde.org> <501D9C36.2040207@missouri.edu> <20120805175106.X3574@besplex.bde.org> <501EC015.3000808@missouri.edu> <20120805191954.GA50379@troutmask.apl.washington.edu> <20120807205725.GA10572@server.rulingia.com> <20120809025220.N4114@besplex.bde.org> <5027F07E.9060409@missouri.edu> <20120814003614.H3692@besplex.bde.org> <50295F5C.6010800@missouri.edu> <20120814072946.S5260@besplex.bde.org> <50297CA5.5010900@missouri.edu> <50297E43.7090309@missouri.edu> <20120814201105.T934@besplex.bde.org> <502A780B.2010106@missouri.edu> <20120815223631.N1751@besplex.bde.org> <502C0CF8.8040003@missouri.edu> <20120906221028.O1542@besplex.bde.org> <5048D00B.8010401@missouri.edu> <504D3CCD.2050006@missouri.edu> <504FF726.9060001@missouri.edu> <20120912191556.F1078@besplex.bde.org> <20120912225847.J1771@besplex.bde.org> <50511B40.3070009@missouri.edu> <20120913204808.T1964@besplex.bde.org>

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> % rcexp: max_er = 0x1658ca3e2ce252 11716177.9430, avg_er = 0.197,
> #>=1:0.5 = 15750254:115895992
>
> Everything except this works fairly well.  cexp() passed tests on only
> 2**12 x 2**12 args.

Do you have any idea why you are getting this huge error?

All I could think of is that cos(y) or sin(y) is subnormal, and exp(x) 
is large.  Is it possible for sin(y) or cos(y) to be subnormal if, say, 
y is close to a non-zero multiple of PI/2?  In other words, can rem_pio2 
give subnormal result (unless of course y is subnormal, but I would 
think that wouldn't generate the above error).



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