Hi, Ignacio. Performance tuning in clojure being somewhat complicated, I would look for prior art here. For instance, the suggestions above give me a 6x speedup, but it's still *way* slower than the equivalent java code. So I used Prismatic's hiphip (array)! library on your problem (but with longs) and got close to java for-loop speed:
https://github.com/Prismatic/hiphip They are focused on numerics, so they don't have support for bytes/shorts, but it looks like you could add that fairly easily. Or maybe someone has already written a equivalent library for bit-twiddling. I would look/ask around. If you're interested, the main slowdown in the above suggestions is probably the extra work from safe typecasts clojure does. The hiphip library uses the unsafe equivalents from clojure.lang.RT. Cheers, Leif On Thursday, March 13, 2014 1:26:33 AM UTC-4, Ignacio Corderi wrote: > > Hey guys, here is a huge performance problem I'm trying to figure out: > > ;; Say you have 2 data arrays sitting out there of 1 MB > > (def one-mb (byte-array (* 1024 1024))) > (def another-mb (byte-array (* 1024 1024))) > > ;; and another one that should have the byte-by-byte XOR of the previous > two > > (def out-mb (byte-array (* 1024 1024))) > > ;; question is... how do you code this guy, so that it doesn't take forever > > (defn inplace-xor [a b out] > (def ln (count a)) > (loop [x 0] > (if (< x ln) > (do > (aset-byte out x (bit-xor (nth a x) (nth b x))) > (recur (+ x 1)) > )))) > > ;; checking the time > > (time (inplace-xor one-mb another-mb out-mb)) > > ;; takes about ~400ms which is.... well... A LOT > > ;; I'm happy to receive a solution that involves calling some java > library... > > Thanks in advance! > -Ignacio > > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
