------- Comment #10 from fxcoudert at gcc dot gnu dot org 2008-03-04 14:21 ------- A bit of experimentation reveals that we can use the asymptotic expression at http://en.wikipedia.org/wiki/Error_function#Asymptotic_expansion for arguments larger than 7, and it does converge with less than 100 terms (for x86 long double, arg = 7.0 requires 30 terms, arg = 8.0 requires 22, arg = 10.0 requires 16 and arg = 18.0 requires 10 terms; allow a bit more for ppc long doubles). So, I rank this as costly but doable, and we frankly don't care too much about the cost at the moment (people relying on heavy simplification of ERFC_SCALED intrinsic, well... I don't see that coming too soon). For smaller arguments, using mpfr_erfc and mpfr_exp should be fine. Does that sound like a plan?
-- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33197
