Simon: if I understand what you're suggesting, you'd like to add a "rounding direction" flag whenever the ubit is set that would indicate which direction you *would* round if you wanted to? I like this idea, as it allows you to throw away the implicit open interval in favor of a rounded exact value (if that's what you want). You potentially get the best of both worlds, but with the speed/memory penalty of setting that extra bit? I can't really comment yet on how much processing this would add...
On Thu, Jul 30, 2015 at 9:18 AM, Simon Byrne <simonby...@gmail.com> wrote: > On Wednesday, 29 July 2015 22:07:45 UTC+1, Steven G. Johnson wrote: >> >> And I don't see a clear practical use-case for an inexact bit per value, >> as opposed to a single inexact flag for a whole set of computations (as in >> IEEE). >> > > Probably not quite what others had in mind, but an instruction-specific > inexact flag (and rounding mode) would make it possible to implement > round-to-odd fairly neatly (e.g., see here > <http://www.exploringbinary.com/gcc-avoids-double-rounding-errors-with-round-to-odd/>), > which would in turn allow implementing all the "formatOf" operations in the > IEE754-2008 standard. >
