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

 

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