Measuring clojurescript performance with KLIPSE

Mar 29, 2016 • Yehonathan Sharvit

Let’s say that you want to profile a piece of code in clojurescript. There is a cool macro for that in clojurescript: time.

time evaluates an expression and prints the time it took and returns the value of the expression.

The interesting question is:

Where does time print the time it took?

Usually, it prints in the browser console. This is because, you have probably called (enable-console-print!) somewhere in your code.

But as a KLIPSE user, you want the time to be displayed in the evaluation rectangle instead of inside the console.

It’s simple to achieve that using with-out-str.

Let’s see it in action by comparing the running time of two naive implementations for prime number generation.

Here is a very naive implementation:

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(defn is-prime? [n]

  (empty? (filter #(= 0 (mod n  %)) (range 2 n))))

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(defn nth-prime [n]

  (last (take n (filter #(is-prime? %) (iterate inc 2)))))

​

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(with-out-str (time (nth-prime 50)))

the evaluation will appear here (soon)...

And now a less naive implementation:

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(defn is-prime-opt? [n]

  (or (= 2 n)

      (not-any? #(= 0 (mod n %)) (range 3 (inc (Math/sqrt n)) 2))))

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(defn nth-prime-opt [n]

  (last (take n (filter #(is-prime-opt? %) (cons 2 (iterate (partial + 2) 3))))))

​

​

(with-out-str (time (nth-prime-opt 50)))

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the evaluation will appear here (soon)...

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