Date: Wed, 2 Mar 2005 15:36:28 +0100 From: Alexander Leidinger <Alexander@Leidinger.net> To: David Schultz <das@freebsd.org> Cc: cvs-all@freebsd.org Subject: Re: cvs commit: src/lib/msun/src e_expf.c Message-ID: <20050302153628.xf36f2rgyss0sk04@netchild.homeip.net> In-Reply-To: <20050226023149.GA63314@VARK.MIT.EDU> References: <200502240632.j1O6WDP9029589@repoman.freebsd.org> <20050226023149.GA63314@VARK.MIT.EDU>
next in thread | previous in thread | raw e-mail | index | archive | help
David Schultz <das@freebsd.org> wrote: > This is related to a good reason why we can't switch the default > precision on i386 to extended. Many of the functions in libm use > minimax approximations, which are ``optimal'' approximations in > the sense that their maximum error over all in-range inputs is the > smallest possible (unless more terms are used). These approximations > take rounding error into account, so when the machine precision is > increased, they're no longer optimal and the error in the approximation > can increase significantly. There are less efficient methods that > don't depend on the exact machine precision, e.g. Chebyshev > approximations, but it would be a PITA to switch everything. What's the problem with recomputing the minimax approximations for extended precision? Is there no tool available to compute them so it is more work than you are willing/able to do ATM? Or is it the amount of computing time needed to recompute the approximations? Bye, Alexander. -- http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7 http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID = 72077137 softy n. [IBM] Hardware hackers' term for a software expert who is largely ignorant of the mysteries of hardware.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050302153628.xf36f2rgyss0sk04>