Date: Wed, 6 Mar 2019 10:48:29 -0800 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Bruce Evans <brde@optusnet.com.au> Cc: freebsd-numerics@freebsd.org Subject: Re: Update ENTERI() macro Message-ID: <20190306184829.GA44023@troutmask.apl.washington.edu> In-Reply-To: <20190306225811.P2731@besplex.bde.org> References: <20190226191825.GA68479@troutmask.apl.washington.edu> <20190227145002.P907@besplex.bde.org> <20190227074811.GA75972@troutmask.apl.washington.edu> <20190227201214.V1823@besplex.bde.org> <20190227161906.GA77785@troutmask.apl.washington.edu> <20190228060920.R4413@besplex.bde.org> <20190304212159.GA12587@troutmask.apl.washington.edu> <20190305153243.Y1349@besplex.bde.org> <20190306055201.GA40298@troutmask.apl.washington.edu> <20190306225811.P2731@besplex.bde.org>
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On Wed, Mar 06, 2019 at 11:56:23PM +1100, Bruce Evans wrote: > On Tue, 5 Mar 2019, Steve Kargl wrote: > > > ... > > I think I have the s_cexpl.c file fixed to use LDBL_EXTRACT_WORDS > > instead of the new macro I introduced. I however cannot figure > > out what David Das did to arrive at k_exp.c, so I cannot write > > Davvid A S. Whoops, again. Seems I conflated real name and login name. > > a similar k_cexpl.c. Yes, I added the 'c' in the name to avoid > > confusion in ld80/. In particular, I have no idea how he found > > his scaling value 'k'. Any insights? > > bde already wrote __ldexp_cexpl() in ld*/k_expl.h, and kargl committed > it in r260066. Does it not work? :-). > > Well, it hasn't been tested, and it indeed cannot work since it spells > cosl(y) as cos(y). Taking long breaks from pecking at libm issues seems to be conducive to memory loss. I'll go review k_expl.h. I simply remember it as having a kernel for expl(). > It is written in a more portable way than the double and float versions > using '1' instead of bit fiddling to start the construction of 2**k. > This makes it identical in ld80 and ld128 (since the exponent range > is the same and the accessor macros hide enough details of the bit > fiddling for the exponent). The duplication is noted in a comment, > but the comment also says that using scalbnl() ond ld128 is probably > best after all (it is slow, but multiplication is also slow). > > I have rewritten the double and float versions in work related to > fixing the accuracy of the double and float versions of hyperbolic > functions. I fixed these before writing the long double hyperbolic > functions using identical methods. You committed the latter, but > the double and float versions still use the old innaccurate slower > methods. > > The rewrite improves the comments, and it is the improved comments > that the reference to k_exp.c in k_expl.h is supposed to be for. > > XX Index: k_exp.c Any chance you'll get around to committing your WIP? Yes, I know you have a few thousand kernel patches in your queue above libm patches. :-) BTW, for the non-exceptional cases with 1M random z values where z=x+Iy and -11350 < x,y < 11350 and I only consider results that are normal, I find my cexpl() yields % ./testl -u -X 11350 Max ULP Re: 1.980535 z = (1.22918109220546510585e+03,1.03853909865862542237e+04) libm = (5.06780736805320166327e+533,-4.39418989082799451477e+533) mpfr = (5.06780736805320166270e+533,-4.39418989082799451456e+533) Max ULP Im: 2.022155 z = (4.83490728165160559637e+03,1.07778990242305355345e+04) libm = (-3.66535128319537945953e+2099,4.67021177841072936494e+2099) mpfr = (-3.66535128319537945915e+2099,4.67021177841072936441e+2099) For comparison, cexp() with -705 < x,y < 705 yields % ./testd -u -X 705 Max ULP Re: 2.215132 z = (1.49377521822925502e+02,1.79997882645095970e+01) libm = (4.93720465697268180e+64,-5.61754869856313932e+64) mpfr = (4.93720465697268310e+64,-5.61754869856313987e+64) Max ULP Im: 2.182779 z = (2.50664219501672335e+02,-4.81327697040560906e+02) libm = (-5.73256778461974670e+108,4.48612518733245315e+108) mpfr = (-5.73256778461974754e+108,4.48612518733245429e+108) Certainly, not exhaustive but encouraging. -- Steve
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