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
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