(42) Double precision summation and DOT

[Werner]

(04-14-2020 02:35 PM)Albert Chan Wrote:  

Quote:0.9 SQRT X^2 0.9 - produces 10^-n, where n=12 for a real 42S and 34 for Free42 Decimal.

This is just lucky. For decimal precision P, many times it just return 0.
Kahan suggest a better way, "Matlab’s Loss is Nobody’s Gain", page 5

ULP = abs((4/3 - 1)*3 – 1)

Hello Albert.
No, it isn't lucky ;-) I specifically looked for a single invertable function that worked for n=12 and n=34. It doesn't have to work for anything else (well, to work for the binary version as well I had to take something else, still 'simple'.
Kahan's example is longer to code.. that is important to me ;-)
Thanks for your insights.. always a joy to read.
Cheers, Werner