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Saturday, September 12, 2009

threads and transactional memory

This beautiful program is straight from the clojure docs: It creates nvecs vectors of nitems numbers, e.g. [1 2 3][4 5 6][7 8 9] and then runs nthreads threads in parallel, swapping numbers from vector to vector niters times

(defn run [nvecs nitems nthreads niters]
  (let [vec-refs (vec (map (comp ref vec)
                           (partition nitems (range (* nvecs nitems)))))
        swap #(let [v1 (rand-int nvecs)
                    v2 (rand-int nvecs)
                    i1 (rand-int nitems)
                    i2 (rand-int nitems)]
                 (let [temp (nth @(vec-refs v1) i1)]
                   (alter (vec-refs v1) assoc i1 (nth @(vec-refs v2) i2))
                   (alter (vec-refs v2) assoc i2 temp))))
        report #(do
                 (prn (map deref vec-refs))
                 (println "Distinct:"
                          (count (distinct (apply concat (map deref vec-refs))))))]
    (dorun (apply pcalls (repeat nthreads #(dotimes [_ niters] (swap)))))

1 comment:

  1. Damn , I recently found this blog. It's really awesome , keep it up!