timespacex'|. 281474976710656&|@*/\.<.1+2*i.-2^12' 0.00096 331904 (281474976710656&|@*/\x:1+2*i.2^5) -: |. 281474976710656&|@*/\.<.1+2*i.-2^5 1
I hope this helps, -- Raul On Tue, May 16, 2017 at 10:31 AM, 'Mike Day' via Programming <[email protected]> wrote: > Thanks again, Raul. > > Well - I'd actually meant ~2^24 odd numbers, 1... _1+2^25 - trust me > to make a mistake in trying to simplify the presentation! Let's call it > a typo. > > I don't think my post was a spoiler, as the problem needs quite a bit > of insight elsewhere; this array helps in getting the answer. > > You're right, of course, for that expression, ~50 seconds on this laptop, > which produces one extended scalar result, but unfortunately I need the > whole vector of cumulative products, 1 3 15 105... > > These time and space tests are for lower size arrays: > 1 ts'281474976710656&|@*/\x:1+2*i.2^10' > > 1.90882 628864 > > 1 ts'datatype 281474976710656&|@*/\x:1+2*i.2^11' > > 7.91167 1.25146e6 > > 1 ts'q =: 281474976710656&|@*/\x:1+2*i.2^12' > > 30.8606 2.49638e6 > > 7!:5<'q' NB. space required for ~2^12 extended elements. > > 589824 > > 2 10 >.@^.589824 NB. rounded up log 2 & log 10 space. > > 20 6 > > > So 2^24 elements are likely to need around 2^40, 10^12 bytes. > This laptop only has about 16GB. > > > So, I think the cludgy "cumoddprod" or its like remains the > answer for a few more Moore cycles! > > Thanks, > > > Mike > > On 16/05/2017 13:44, Raul Miller wrote: >> >> Forgive me for asking, but isn't 33554431 = _1+2^25 ? >> >> Anyway, this seems to work for me: >> >> 281474976710656&|@*/x:1+2*i.2^23 >> >> I'll leave out the answer, out of respect for project euler (though >> maybe the rules allow that now?). >> >> timespacex'281474976710656&|@*/x:1+2*i.2^23' >> 12.457 1.67937e9 >> >> ... and needs about 13 seconds and about 2 gig ram. >> >> That said, I suppose it would be nice if x m&|@* y worked reliably for >> fixed precision integers x, m and y >> >> Thanks, >> > > > > --- > 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
