Mill Computing, Inc. Forums The Mill Architecture Floating Point Rounding Reply To: Floating Point Rounding

Witold Baryluk
Post count: 33

Adding to my previous reply that explicit per-instruction rounding modes are important, and good. I was wondering if it would be possible to extend it even further for vector operations. Even in AVX-512, the rounding mode specified in instruction applies the same way to all operands (vector elements). However, ability to do 3 different roundings in one vector op (towards minus infinity, towards plus infinity, and towards nearest), could make the interval arithmetic implementations even nicer and so much faster. 2 additional bits per operand might be a bit too much to fit into op, but a special “ALL” mode, where for two-element vectors is interpreted as (-INF, +INF), and for 4 element vectors as (-INF, NEAR, +INF, ZERO) for respective operands would be awesome. This combined with vector shuffling / permutations and expands, would make implementations of interval arithmetic rather straightforward, and really fast.