See https://code.jsoftware.com/wiki/Vocabulary/IFamily#Performance .
Tolerant i.-family operations on arrays are tough. They end up doing sequential search. ~.!.0 will be much faster, if you don't need the tolerance.
Henry Rich On 8/29/2023 8:47 PM, Ben Gorte wrote:
Dear J, I noticed that ~. (nub) can become very slow on float arrays - is that known? Mine was a 9 million times 6 array and it seemed to hang on my laptop. This can be demonstrated as: idx =: 4$.$.10 10 10 10 10 10$1 NB. a million different tuples of 6 integers 6!:2 'echo $ ~. idx' 1000000 6 0.068726 fdx =. 0.0+idx NB. now with floats: 6!:2 'echo $ ~. fdx' 1000000 6 225.568 JVERSION Engine: j9.4.1/j64/linux Build: commercial/2023-02-27T15:21:43/clang-11-0-0/SLEEF=1 Library: 9.4.21 Qt IDE: 2.0.3/5.12.8(5.15.3) Platform: Linux 64 Installer: j9.4 install InstallPath: /home/ben/j9.4 Contact: www.jsoftware.com I haven't tried other J versions, except the (current) playground in Firefox. There it is similar. Other than that I am continuing to enjoy J, daily. Greetings, Ben ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
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