Date: Mon, 28 Nov 2005 04:58:57 +0000 (UTC) From: Bruce Evans <bde@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/lib/msun/src e_lgammaf_r.c k_cosf.c k_sinf.c math_private.h s_cosf.c s_sinf.c Message-ID: <200511280458.jAS4wvTq049496@repoman.freebsd.org>
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bde 2005-11-28 04:58:57 UTC FreeBSD src repository Modified files: lib/msun/src e_lgammaf_r.c k_cosf.c k_sinf.c math_private.h s_cosf.c s_sinf.c Log: Use only double precision for "kernel" cosf and sinf (except for returning float). The functions are renamed from __kernel_{cos,sin}f() to __kernel_{cos,sin}df() so that misuses of them will cause link errors and not crashes. This version is an almost-routine translation with no special optimizations for accuracy or efficiency. The not-quite-routine part is that in __kernel_cosf(), regenerating the minimax polynomial with double precision coefficients gives a coefficient for the x**2 term that is not quite -0.5, so the literal 0.5 in the code and the related `hz' variable need to be modified; also, the special code for reducing the error in 1.0-x**2*0.5 is no longer needed, so it is convenient to adjust all the logic for the x**2 term a little. Note that without extra precision, it would be very bad to use a coefficient of other than -0.5 for the x**2 term -- the old version depends on multiplication by -0.5 being infinitely precise so as not to need even more special code for reducing the error in 1-x**2*0.5. This gives an unimportant increase in accuracy, from ~0.8 to ~0.501 ulps. Almost all of the error is from the final rounding step, since the choice of the minimax polynomials so that their contribution to the error is a bit less than 0.5 ulps just happens to give contributions that are significantly less (~.001 ulps). An Athlons, for uniformly distributed args in [-2pi, 2pi], this gives overall speed increases in the 10-20% range, despite giving a speed decrease of typically 19% (from 31 cycles up to 37) for sinf() on args in [-pi/4, pi/4]. Revision Changes Path 1.8 +6 -6 src/lib/msun/src/e_lgammaf_r.c 1.14 +11 -12 src/lib/msun/src/k_cosf.c 1.12 +11 -13 src/lib/msun/src/k_sinf.c 1.20 +2 -2 src/lib/msun/src/math_private.h 1.12 +7 -19 src/lib/msun/src/s_cosf.c 1.12 +7 -19 src/lib/msun/src/s_sinf.c
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