On Dec 11, 2014 11:13 AM, "Ilia Mirkin" <<a href="mailto:imirkin@alum.mit.edu">imirkin@alum.mit.edu</a>> wrote: > > On Thu, Dec 11, 2014 at 2:10 PM, Chris Forbes <<a href="mailto:chrisf@ijw.co.nz">chrisf@ijw.co.nz</a>> wrote: > > Iago, > > > > This doesn't matter for GL conformance -- but the impression I get is > > that dEQP is aiming at something more. > > > > In any case, the usual problem with this is inaccurate range > > reduction, which is fixable in software at some performance cost. The > > C library does this, for example. > > Probably related to this: > ><a href="https://randomascii.wordpress.com/2014/10/09/intel-underestimates-error-bounds-by-1-3-quintillion/"> https://randomascii.wordpress.com/2014/10/09/intel-underestimates-error-bounds-by-1-3-quintillion/</a> That's a fun article, but beside the point for what we probably care about. No one cares about precisely computing sin(pi) to hundreds of decimal places on a GPU. If we really want to fix the issue, we can do range reduction at the cost of probably a couple extra instructions. That said, I doubt this will be an issue in real life as x % pi begins to get fairly imprecise at those magnitudes.