Date: Thu, 13 Apr 2017 10:12:48 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: freebsd-numerics@freebsd.org Cc: freebsd-standards@freebsd.org Subject: Re: Implementation of half-cycle trignometric functions Message-ID: <20170413171248.GA86780@troutmask.apl.washington.edu> In-Reply-To: <20170409220809.GA25076@troutmask.apl.washington.edu> References: <20170409220809.GA25076@troutmask.apl.washington.edu>
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On Sun, Apr 09, 2017 at 03:08:09PM -0700, Steve Kargl wrote:
> Both IEEE-754 2008 and ISO/IEC TS 18661-4 define the half-cycle
> trignometric functions cospi, sinpi, and tanpi. The attached
> patch implements cospi[fl], sinpi[fl], and tanpi[fl]. Limited
> testing on the cospi and sinpi reveal a max ULP less than 0.89;
> while tanpi is more problematic with a max ULP less than 2.01
> in the interval [0,0.5]. The algorithms used in these functions
> are documented in {ks}_cospi.c, {ks}_sinpi.c, and s_tanpi.c.
>
> Note 1. ISO/IEC TS 18661-4 says these funstions are guarded by
> a predefine macro. I have no idea or interest in what clang and
> gcc do with regards to this macro. I've put the functions behind
> __BSD_VISIBLE.
>
> Note 2. I no longer have access to a system with ld128 and
> adequate support to compile and test the ld128 implementations
> of these functions. Given the almost complete lack of input from
> others on improvements to libm, I doubt that anyone cares. If
> someone does care, the ld128 files contain a number of FIXME comments,
> and in particular, while the polynomial coefficients are given
> I did not update the polynomial algorithms to properly use the
> coefficients.
>
> The code is attached the bug reportr.
>
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=218514
>
While everyone is busy reviewing and testing the patch available
in bugzilla, I suspect some may be wondering about the inverse
half-cycle trignometric functions. I have worked out an algorithm
for asinpi[fl] and have a working implemenation of asinpif(x).
It will take a couple of weeks (due to limited available time)
before I can submit asinpi[fl], acospi[fl], and atanpi[fl], but
work is in progress.
--
Steve
20161221 https://www.youtube.com/watch?v=IbCHE-hONow
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