Date: Sun, 9 Apr 2017 15:08:09 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: freebsd-numerics@freebsd.org Subject: Implementation of half-cycle trignometric functions Message-ID: <20170409220809.GA25076@troutmask.apl.washington.edu>
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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
--
Steve
20161221 https://www.youtube.com/watch?v=IbCHE-hONow
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