On Mon, Nov 14, 2022 at 07:30:18AM -0700, Jeff Law via Gcc-patches wrote:
> To Jakub's concern. I thought sqrt was treated like +-/* WRT accuracy
> requirements by IEEE. ie, for any input there is a well defined answer for
> a confirming IEEE implementation. In fact, getting to that .5ulp bound is
> a significant amount of the cost for a NR or Goldschmidt (or hybrid)
> implementation if you've got a reasonable (say 12 or 14 bit) estimator and
> high performance fmacs.
That might be the case (except for the known libquadmath sqrtq case
PR105101 which fortunately is not a builtin).
But we'll need to ulps infrastructure for other functions anyway and
it would be nice to write a short testcase first that will test
sqrt{,f,l,f32,f64,f128} and can be easily adjusted to test other functions.
I'll try to cook something up tomorrow.
Jakub
