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| author | zimmerma <zimmerma@280ebfd0-de03-0410-8827-d642c229c3f4> | 2021-02-02 15:31:06 +0000 |
|---|---|---|
| committer | zimmerma <zimmerma@280ebfd0-de03-0410-8827-d642c229c3f4> | 2021-02-02 15:31:06 +0000 |
| commit | 0a9ec50b24ca5048b0ff4cbd3449017fa026289c (patch) | |
| tree | c476327f39727f1438516fbebad7052236e3f22d /src/atan2u.c | |
| parent | 7710b56a9b7d26e3d49bb1c0a889f9e2222d4087 (diff) | |
| download | mpfr-0a9ec50b24ca5048b0ff4cbd3449017fa026289c.tar.gz | |
[src/atan2u.c] fixed atan2u with respect to the four quadrants
[tests/tatan2u.c] added corresponding non-regression tests
git-svn-id: https://scm.gforge.inria.fr/anonscm/svn/mpfr/trunk@14321 280ebfd0-de03-0410-8827-d642c229c3f4
Diffstat (limited to 'src/atan2u.c')
| -rw-r--r-- | src/atan2u.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/src/atan2u.c b/src/atan2u.c index cccf54d29..4054aa216 100644 --- a/src/atan2u.c +++ b/src/atan2u.c @@ -190,9 +190,15 @@ mpfr_atan2u (mpfr_ptr z, mpfr_srcptr y, mpfr_srcptr x, unsigned long u, { mpfr_exp_t expt, e; /* atan2u(-y,x,u) = -atan(y,x,u) - atan2u(y,x,u) = atan(y/x)*u/(2*pi) for x > 0 - atan2u(y,x,u) = u/2-atan(-y/x)*u/(2*pi) for x < 0 */ + atan2u(y,x,u) = atan(|y/x|)*u/(2*pi) for x > 0 + atan2u(y,x,u) = u/2-atan(|y/x|)*u/(2*pi) for x < 0 + atan2pi atan2u + First quadrant: [0,1/2] [0,u/4] + Second quadrant: [1/2,1] [u/4,u/2] + Third quadrant: [-1,-1/2] [-u/2,-u/4] + Fourth quadrant: [-1/2,0] [-u/4,0] */ inex = mpfr_div (tmp, y, x, MPFR_RNDN); + MPFR_SET_SIGN (tmp, 1); expt = MPFR_GET_EXP(tmp); /* |tmp - y/x| <= e1 := 1/2*ulp(tmp) = 2^(expt-prec-1) */ inex |= mpfr_atanu (tmp, tmp, u, MPFR_RNDN); @@ -220,6 +226,8 @@ mpfr_atan2u (mpfr_ptr z, mpfr_srcptr y, mpfr_srcptr x, unsigned long u, now we want error <= 2^(expt-prec+err) thus err = e-expt */ e -= MPFR_GET_EXP(tmp); + if (MPFR_SIGN(y) < 0) /* atan2u is odd with respect to y */ + MPFR_CHANGE_SIGN(tmp); if (MPFR_LIKELY (MPFR_CAN_ROUND (tmp, prec - e, MPFR_PREC (z), rnd_mode))) break; |