On Tue, Oct 23, 2018 at 10:37:54AM +0000, Wilco Dijkstra wrote:
> >> So I think the runtime math libraries shoot for .5 ULP (yes, they don't
> >> always make it, but that's their goal). We should probably have the
> >> same goal. Going from 0 to 2 ULPs would be considered bad.
>
> Generally the goal is 1ULP in round to nearest
Has that changed recently? At least in the past for double the goal has
been always .5ULP in round to nearest.
> > But we do that everywhere (with -funsafe-math-optimizations or
> > -fassociative-math).
>
> Exactly. And 2 ULP is extremely accurate for fast-math transformations - much
> better than eg. reassociating additions.
For -ffast-math yeah.
Jakub
