Hi, >> 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.
Yes. 0.5 ULP (perfect rounding) as a goal was insane as it caused ridiculous slowdowns in the 100000x range for no apparent reason. GLIBC was black listed in the HPC community as a result. So I removed most of the perfect rounding code - this not only avoids the slowdown but also speeds up the average case significantly. The goal is to stay below 1 ULP, the math functions Szabolcs and I rewrote generally do better, eg sinf is 0.56 ULP. Wilco
