If one digs long enough, Kahan pops up. Inverse square root. - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: Not HP Calculators (/forum-7.html) +--- Forum: Not remotely HP Calculators (/forum-9.html) +--- Thread: If one digs long enough, Kahan pops up. Inverse square root. (/thread-20584.html) |
If one digs long enough, Kahan pops up. Inverse square root. - pier4r - 10-03-2023 07:37 AM We all know that W. Kahan (the author of many numerical solutions for the HP calculators) was great, but I was surprised to learn that he was behind the inverse square root solution. https://www.netlib.org/fdlibm/e_sqrt.c (point B) , this is related to the FISR problem. What I find funny (and sad) is that somehow people think that back then people were plain stupid or without equipment. A comment on youtube notice this when another user pointed out Kahan "It's still quite a feat to acquire that knowledge back in the day." (as if today would be easy to discover the solution) I'd argue it is harder today to find such solutions, because nowadays people just throw hardware at the problem before optimizing (I am guilty of this). In the past they needed to optimize more given the limited HW. RE: If one digs long enough, Kahan pops up. Inverse square root. - EdS2 - 10-03-2023 07:45 AM Nice find! From the comment block in the linked code: Code: (This is a copy of a drafted paper by Prof W. Kahan RE: If one digs long enough, Kahan pops up. Inverse square root. - Joe Horn - 10-03-2023 02:18 PM (10-03-2023 07:37 AM)pier4r Wrote: We all know that W. Kahan (the author of many numerical solutions for the HP calculators) was great ... ... and still is: https://en.wikipedia.org/wiki/William_Kahan RE: If one digs long enough, Kahan pops up. Inverse square root. - pier4r - 10-03-2023 02:35 PM (10-03-2023 02:18 PM)Joe Horn Wrote: ... and still is: https://en.wikipedia.org/wiki/William_Kahan Yes sorry, I wanted to mean for the work he has done. Not that he was dead (I always mixed up this part of the English language) RE: If one digs long enough, Kahan pops up. Inverse square root. - Wes Loewer - 10-09-2023 03:53 AM (10-03-2023 07:37 AM)pier4r Wrote: What I find funny (and sad) is that somehow people think that back then people were plain stupid or without equipment. I had the opposite reaction from a Geometry student once. When I was explaining how the Greeks figured it all out without calculators or computers, one student replied, "Wow, they were really smart back then." Indeed they were. |