Date: Thu, 5 Dec 2013 20:06:22 +0100 From: Filipe Maia <filipe.c.maia@gmail.com> To: Steve Kargl <sgk@troutmask.apl.washington.edu>, freebsd-numerics@freebsd.org Subject: Re: dead code in lgamma_r[f]? Message-ID: <CAN5hRiV6N1arc4RDv=9JbRiXp-J9o3WzAbeZSOpAxks2ZeG%2B_w@mail.gmail.com> In-Reply-To: <20131205182324.GA65135@troutmask.apl.washington.edu> References: <20131205173700.GA64575@troutmask.apl.washington.edu> <20131205182324.GA65135@troutmask.apl.washington.edu>
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What if ix == 0x433xxxxx?
Wouldn't the if clause be false?
On Thu, Dec 5, 2013 at 7:23 PM, Steve Kargl <
sgk@troutmask.apl.washington.edu> wrote:
> On Thu, Dec 05, 2013 at 09:37:00AM -0800, Steve Kargl wrote:
> > In reviewing the implementation details for lgamma_r[f],
> > I noticed that in src/e_lgamma.c (and similar code in
> > e_lgammaf.c):
>
> These should be e_lgamma_r.c and e_lgammaf_r.c.
> I've only done some limited testing, but the
> patch following my sig seems to work.
>
> Note the first part of the diff allows us to remove the
> cast to float in e_lgamma_r.c, which minimizes the diff
> between e_lgamma_r.c and e_lgammaf_r.c (and e_lgammal_r.c :).
>
> --
> Steve
>
> Index: src/e_lgamma_r.c
> ===================================================================
> --- src/e_lgamma_r.c (revision 1427)
> +++ src/e_lgamma_r.c (working copy)
> @@ -173,19 +173,15 @@
> */
> z = floor(y);
> if(z!=y) { /* inexact anyway */
> - y *= 0.5;
> - y = 2.0*(y - floor(y)); /* y = |x| mod 2.0 */
> - n = (int) (y*4.0);
> + y /= 2;
> + y = 2*(y - floor(y)); /* y = |x| mod 2.0 */
> + n = (int)(y*4);
> } else {
> - if(ix>=0x43400000) {
> - y = zero; n = 0; /* y must be even */
> - } else {
> - if(ix<0x43300000) z = y+two52; /* exact */
> - GET_LOW_WORD(n,z);
> - n &= 1;
> - y = n;
> - n<<= 2;
> - }
> + z = y+two52; /* exact */
> + GET_LOW_WORD(n,z);
> + n &= 1;
> + y = n;
> + n<<= 2;
> }
> switch (n) {
> case 0: y = __kernel_sin(pi*y,zero,0); break;
> Index: src/e_lgammaf_r.c
> ===================================================================
> --- src/e_lgammaf_r.c (revision 1427)
> +++ src/e_lgammaf_r.c (working copy)
> @@ -106,19 +106,15 @@
> */
> z = floorf(y);
> if(z!=y) { /* inexact anyway */
> - y *= (float)0.5;
> - y = (float)2.0*(y - floorf(y)); /* y = |x| mod 2.0 */
> - n = (int) (y*(float)4.0);
> + y /= 2;
> + y = 2*(y - floorf(y)); /* y = |x| mod 2.0 */
> + n = (int)(y*4);
> } else {
> - if(ix>=0x4b800000) {
> - y = zero; n = 0; /* y must be even */
> - } else {
> - if(ix<0x4b000000) z = y+two23; /* exact */
> - GET_FLOAT_WORD(n,z);
> - n &= 1;
> - y = n;
> - n<<= 2;
> - }
> + z = y+two23; /* exact */
> + GET_FLOAT_WORD(n,z);
> + n &= 1;
> + y = n;
> + n<<= 2;
> }
> switch (n) {
> case 0: y = __kernel_sindf(pi*y); break;
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