For dyad i. use i.&:(1&|."1). Similar applies to other dyadic family members.
On Sat, 26 Nov 2022, Ben Gorte wrote:
Hi Henry, could you be a bit more explicit about these 32 bits + workaround? Eliahs suggestion helps, but doesn't seem to solve the entire issue. For example, something similar occurs in dyadic i. Thanks, Ben On Fri, 25 Nov 2022 at 02:57, Henry Rich <henryhr...@gmail.com> wrote:It's a data dependency: xxx1 =. 1 ,"1~ 10000 3?@$ 100 6!:2'~. xxx1' 0.0068845 xxx1 =. 1 ,"1~ 10000 3?@$ 10000 6!:2'~. xxx1' 0.000578 Repetitions at lengths of 32 bits seem to be trouble (not surprising when you think about it). One kludgy-smelling workaround would be to rotate the value of each word by a varying number of bits. The advantage of that is that it requires very little setup and would still be fast for short arguments. You have been looking into better hash functions. Do you want to implement one here? Preferably one that is very fast for short arguments. hhr On 11/24/2022 12:40 AM, Elijah Stone wrote: > That looks rather serious. It seems some problem with the hashing > function is causing an unreasonably high rate of collisions. As a > temporary workaround, you can try using ~.&.:(1&|."1), or use the > 32-bit version. > > On Thu, 24 Nov 2022, Ben Gorte wrote: > >> G'day, >> >> >> Still J-ing along, I believe I ran into a little performance issue. >> >> I can strip it down into: >> >> >> A3=:?1000000 3$100 NB. three columns of random numbers 0 .. 99 >> >> A31 =: A3,.1 NB. with an extra column of 1-s >> >> A4=:?1000000 4$100 NB. or four random columns >> >> 6!:2 'echo $~.A3' >> >> 632783 3 >> >> 0.037673 >> >> 6!:2 'echo $~.A31' >> >> 632783 4 >> >> 24.6091 >> >> That's 600 times longer! >> >> >> However, >> >> 6!:2 'echo $~.A4' >> >> 995025 4 >> >> 0.43277 >> >> is again much quicker. >> >> >> This is consistent over versions 807, 903 and 904, all with Ubuntu >> linux. >> >> >> I do need the fourth column and it has many 1-s (not all). >> >> >> Thanks, >> >> Ben >> ---------------------------------------------------------------------- >> 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
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