A 17-bit lookup table for a 17x1024 sized Y would require 16 MB. The 4-bit version is 10kb and would fit into the L1 cache. I believe the L1 vs RAM access times are 1-to-60 or so (http://www.7-cpu.com/cpu/Haswell.html).
Of course, maybe we use few enough Xs at any given time that the relevant entries of a 17-bit LUT would be hot anyway. On Thu, Oct 13, 2016 at 8:04 PM, Raul Miller <[email protected]> wrote: > Simplest "high performance" version of that would be to pre-compute each of > the possible answers for each possible X. > > -- > Raul > > > On Thu, Oct 13, 2016 at 9:33 PM, Michal Dobrogost < > [email protected]> wrote: > > > Yes, you can rewrite (+./@:*.) as (+./ . *.). > > > > Hehe, in terms of peculiar ways and unknown reasons, I invite you to > think > > about how you might go about implementing a high-performance version of > > this operation where X and Y are restricted to boolean elements, Y is > > static and X dynamically changes. > > > > On Thu, Oct 13, 2016 at 10:32 AM, Erling Hellenäs < > > [email protected]> > > wrote: > > > > > It is this operation +./ . *. we rewrite in peculiar ways for unknown > > > reasons? > > > > > > [ x=: 1 0 1 1 0 > > > > > > 1 0 1 1 0 > > > > > > [ y=: 5 6 $1 0 0 0 0 0 0 1 0 1 1 0 0 1 0 0 0 1 0 0 0 0 1 1 0 1 1 1 0 1 > > > > > > 1 0 0 0 0 0 > > > > > > 0 1 0 1 1 0 > > > > > > 0 1 0 0 0 1 > > > > > > 0 0 0 0 1 1 > > > > > > 0 1 1 1 0 1 > > > > > > x +./ . *. y > > > > > > 1 1 0 0 1 1 > > > > > > > > > /Erling > > > > > > > > > > > > ---------------------------------------------------------------------- > > > 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
