diff options
| author | vlefevre <vlefevre@280ebfd0-de03-0410-8827-d642c229c3f4> | 2009-09-22 15:51:15 +0000 |
|---|---|---|
| committer | vlefevre <vlefevre@280ebfd0-de03-0410-8827-d642c229c3f4> | 2009-09-22 15:51:15 +0000 |
| commit | 57840fcb92a79b474a0e63d35853ea1b4314833f (patch) | |
| tree | cd095b5d836dcbb74878937f215c7c46a4a79e60 /atan.c | |
| parent | 3ea8c5b8aa91cff96aea82360d55ca072ef9c269 (diff) | |
| download | mpfr-57840fcb92a79b474a0e63d35853ea1b4314833f.tar.gz | |
atan.c: added some assertions.
git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@6484 280ebfd0-de03-0410-8827-d642c229c3f4
Diffstat (limited to 'atan.c')
| -rw-r--r-- | atan.c | 10 |
1 files changed, 7 insertions, 3 deletions
@@ -285,7 +285,7 @@ mpfr_atan (mpfr_ptr atan, mpfr_srcptr x, mpfr_rnd_t rnd_mode) /* since realprec >= 4, n0 >= ceil(log2(8)) >= 3, thus 3*n0 > 2 */ prec = (realprec + sup) + 1 + MPFR_INT_CEIL_LOG2 (3*n0-2); - /* the number of lost bits due to argument reduction is + /* the number of lost bits due to argument reduction is 9 - 2 * EXP(sk), which we estimate by 9 + 2*ceil(log2(p)) since we manage that sk < 1/p */ if (MPFR_PREC (atan) > 100) @@ -315,17 +315,21 @@ mpfr_atan (mpfr_ptr atan, mpfr_srcptr x, mpfr_rnd_t rnd_mode) oldn0 = 3 * (n0 + 1); } + /* The mpfr_ui_div below mustn't underflow. This is guaranteed by + MPFR_SAVE_EXPO_MARK, but let's check that for maintainability. */ + MPFR_ASSERTD (__gmpfr_emax <= 1 - __gmpfr_emin); + if (comparaison > 0) /* use atan(xp) = Pi/2 - atan(1/xp) */ mpfr_ui_div (sk, 1, xp, MPFR_RNDN); else mpfr_set (sk, xp, MPFR_RNDN); - + /* now 0 < sk <= 1 */ /* Argument reduction: atan(x) = 2 atan((sqrt(1+x^2)-1)/x). We want |sk| < k/sqrt(p) where p is the target precision. */ lost = 0; - for (red = 0; MPFR_EXP(sk) > - (mp_exp_t) log2p; red ++) + for (red = 0; MPFR_GET_EXP(sk) > - (mp_exp_t) log2p; red ++) { lost = 9 - 2 * MPFR_EXP(sk); mpfr_mul (tmp, sk, sk, MPFR_RNDN); |