[New REPL Window] REPL window freezes when the evaluation takes a long time

[PEZ]

When evaluating something that takes ”a sufficiently long time” to evaluate, the REPL window freezes. Evaluating the same thing inline works.

** REPRO **

Below is a naïve implementation of Eratosthenes Sieve. When evaluating the top-level form in that comment form in the REPL window (ctrl+alt+v alt+space) for n = 1000000 on my machine the REPL window never returns with the answer and becomes totally unresponsive.

(defn not-divisible-by [n d]
  (when-not (integer? (/ n d))
    n))

(defn sieve [n]
  (loop [found-primes [2]
         candidates (range 3 (inc n))]
    (let [highest-found-prime (last found-primes)
          remaining (->> candidates
                         (map #(not-divisible-by % highest-found-prime))
                         (remove nil?))]
      (if (= remaining candidates)
        (concat found-primes candidates)
        (recur (conj found-primes (first remaining)) (rest remaining))))))

(comment
  (sieve 1000000))

Again, evaluating the same form inline (ctrl+alt+v space), eventually, the results will be delivered.

Also, closing the REPL window and reopening it again works as a fix for getting the window back in operation.

[PEZ]

Update: It doesn't seem to be about how long time the evaluation takes. If I wrap my run of this test in (time), like so:

eratosthenes=> (time (str "mine: " (count (sieve-refined 1000000)) " primes"))
"Elapsed time: 7845.699169 msecs"
"mine: 78498 primes"

I do get the prompt back (even running this for primes up to 1,000,000).

So now I am guessing it is that the REPL Window chokes on the size of the results.

[cfehse]

So now I am guessing it is that the REPL Window chokes on the size of the results.

This is exactly what happens. The whole output is processed through the Scanner.processLine() method which takes a awful long time.