Mike, thanks for pointing me to that problem - enjoyed it very much including (re-)learning some Combinatorics. It took quite some time to solve, first arriving at the solution and then running it ;). During the aftermath I gained additional insights from the problem thread, especially this: https://projecteuler.net/action=redirect;post_id=397459 With this the solution can be written as a one-liner and returns instantly - posted it to the same thread: https://projecteuler.net/action=redirect;post_id=400448 (additionally, it's a use case for fold F:.) FYI, Stefan
On Mon, May 2, 2022 at 10:23 PM 'Michael Day' via Chat <[email protected]> wrote: > Ed Gottsman, mainly, > > I was so annoyed with the 14+ minutes it took my solution for Euler > Problem 778 to run that > I revamped it to a cleaner, but somewhat more complicated approach. It > was the same > maths, including finite/modular stuff but now avoiding the use or > extended integers: I > eventually got it to work. > > So the new approach runs in ~1.25 seconds and probably uses less memory, > though I haven't > proved that assertion. The disadvantage is of course that it took me > several hours of error- > chasing to achieve the speed-up! > > I can't find my solution to problem 51! There was a time when I'd > solved all of the extant > problems. But they got harder, and I've slowed down, and now have > over 300 in my > unsolved list. > > Cheers, > > Mike > > -------- Forwarded Message -------- > Subject: Re: [Jprogramming] Extended precision question > Date: Mon, 2 May 2022 05:54:46 +0100 > From: Ed Gottsman <[email protected]> > Reply-To: [email protected] > To: [email protected] > > > > Mike, > > Many thanks for the guidance. I’d already determined that my x: > approaches to #66 were going to involve waiting for the earth to crash > into the sun—or, equally unattractive, paying Google Cloud Platform for > a fleet of “Godzilla” class VMs—so I am looking in other directions. I > took a break and went back to Prime Digit Replacements (#51), the > brevity of whose eventual solution filled me with nerd pride :-). (Am I > the only Project Euler J developer who gets a guilty thrill from > reviewing the magnum opuses submitted by other participants?) > > Thanks again. > > Ed > > Sent from my iPad > > > On May 1, 2022, at 8:25 PM, 'Michael Day' via Programming > > <[email protected]> wrote: > > > > Mainly for Ed Gottsman: > > > > Chat really, but the thread is already here. > > > > I've just solved Euler Problem 788 with the assistance of extended > > precision numbers. The solution is > > slow, taking over 14 minutes, but at least it's less than the lifetime > > of the universe, unlike my (projected) > > methods for some of these problems! > > > > It's relatively easy, compared with many of the recent questions; > > https://projecteuler.net/problem=788 . > > > > As for Ed's original post, I'll point out that x: features aren't > > necessary for the solution of problem 66 > > although they can possibly help in understanding it. I don't think > > that's a spoiler. > > > > Cheers, > > > > Mike > > > >> On 21/04/2022 17:43, Ed Gottsman wrote: > >> Hello. > >> I’m working on the Project Euler “Diophantine equation” problem (#66) > >> and using J’s extended precision facilities. I’ve run into behavior > >> that confuses me. Boiled down (and overusing x: just to be sure): > >> x: %: x: 1 + x: *: x: 999999999 > >> 999999999 > >> That is (if my syntax is right), the square root of (one plus the > >> square of a really large n) is n. I’m apparently misunderstanding > >> something about extended precision. I’ve tried it with a variety of > >> uses of x: but to no avail, and as I read the x: documentation…this > >> is an odd result. > >> > >> Any help would be much appreciated. > >> (J901 on iPadOS, for which sincere kudos to Ian Clark.) > >> Many thanks. > >> Ed > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > > > > > > -- This email has been checked for viruses by Avast antivirus software. > > https://www.avast.com/antivirus > > > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
