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Diffstat (limited to 'doc/mpfr.texi')
| -rw-r--r-- | doc/mpfr.texi | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/doc/mpfr.texi b/doc/mpfr.texi index 8de7cad68..167fb6f13 100644 --- a/doc/mpfr.texi +++ b/doc/mpfr.texi @@ -2740,6 +2740,15 @@ created using the GMP @code{gmp_randinit} function (see the GMP manual). Note: the note for @code{mpfr_urandomb} holds too. In addition, the exponent range and the rounding mode might have a side effect on the next random state. + +The rule for the underflow flag is here ``underflow before rounding'' +instead of the usual ``underflow after rounding''. The reason is that +the exponent is drawn first, and if it is smaller than the minimum +exponent, the significand is not drawn. To fix the behavior on the +underflow flag, one would have to draw the significand in some cases, +meaning that the behavior of the random generator would change, thus +it would break the ABI for the MPFR 3.1 branch. However, the observed +behavior always corresponds to an existing number. @end deftypefun @deftypefun int mpfr_grandom (mpfr_t @var{rop1}, mpfr_t @var{rop2}, gmp_randstate_t @var{state}, mpfr_rnd_t @var{rnd}) |