def _ndtr(x): """Implements ndtr core logic.""" dtype = lax.dtype(x).type half_sqrt_2 = dtype(0.5) * np.sqrt(2., dtype=dtype) w = x * half_sqrt_2 z = lax.abs(w) y = lax.select( lax.lt(z, half_sqrt_2), dtype(1.) + lax.erf(w), lax.select(lax.gt(w, dtype(0.)), dtype(2.) - lax.erfc(z), lax.erfc(z))) return dtype(0.5) * y
def erfc(x): x, = _promote_args_inexact("erfc", x) return lax.erfc(x)