The Fastest TwoSum on an Apple M1

In my last post , I pointed out that FastTwoSum plus a sort is actually faster than normal TwoSum on modern hardware, and suggested that TwoSum is therefore obsolete. This post expands the analysis and tests futher optimizations on the Apple M1 chip. General approach The general FastTwoSum algorithm is the following: s = a + b bb = s - a e = b - bb This assumes that |a| > |b| , or perhaps a…