diff options
Diffstat (limited to 'exp.c')
| -rw-r--r-- | exp.c | 11 |
1 files changed, 8 insertions, 3 deletions
@@ -1,6 +1,6 @@ /* mpfr_exp -- exponential of a floating-point number -Copyright 1999, 2000, 2001, 2002, 2003 Free Software Foundation. +Copyright 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation. Contributed by the Spaces project. This file is part of the MPFR Library. @@ -78,14 +78,19 @@ mpfr_exp (mpfr_ptr y, mpfr_srcptr x, mp_rnd_t rnd_mode) /* result is 0 when exp(x) < 1/2*2^(__gmpfr_emin), i.e. x < (__gmpfr_emin-1) * LOG2 */ if (d < ((double) __gmpfr_emin - 1.0) * LOG2) - return mpfr_set_underflow (y, rnd_mode, 1); + { + /* warning: mpfr_set_underflow rounds away for RNDN */ + if (rnd_mode == GMP_RNDN && d < ((double) __gmpfr_emin - 2.0) * LOG2) + rnd_mode = GMP_RNDZ; + return mpfr_set_underflow (y, rnd_mode, 1); + } /* if x < 2^(-precy), then exp(x) i.e. gives 1 +/- 1 ulp(1) */ if (expx < -precy) { int signx = MPFR_SIGN(x); - if (signx < 0 && (rnd_mode == GMP_RNDD || rnd_mode == GMP_RNDZ)) + if (signx < 0 && rnd_mode == GMP_RNDD) { MPFR_CLEAR_FLAGS(y); MPFR_SET_POS(y); |