Clojure

(object-array [1]) is ~3x slower than (object-array (rseq [1]))

Details

  • Type: Defect Defect
  • Status: Closed Closed
  • Priority: Minor Minor
  • Resolution: Completed
  • Affects Version/s: Release 1.4
  • Fix Version/s: Release 1.5
  • Component/s: None
  • Labels:
  • Patch:
    Code and Test
  • Approval:
    Ok

Description

{{user=> (time (dotimes [_ 10000000] (object-array [1])))
"Elapsed time: 1178.116257 msecs"
nil
user=> (time (dotimes [_ 10000000] (object-array (rseq [1]))))
"Elapsed time: 422.42248 msecs"
nil}}

This appears to be because PersistentVector$ChunkedSeq does not implement Counted, so RT.count is iterating the ChunkedSeq to get its count.

Activity

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Stuart Halloway added a comment -

Two patches to be applied together, the 10/19 patch adds tests and updates to latest test.generative.

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Stuart Halloway added a comment - Two patches to be applied together, the 10/19 patch adds tests and updates to latest test.generative.
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Tassilo Horn added a comment -

This patch makes PersistentVector$ChunkedSeq implement Counted.

Performance before:

(let [v (vec (range 10000))
      vs (seq v)]
  (time (dotimes [_ 10000]
          (count v)))
  (time (dotimes [_ 10000]
          (count vs))))
;"Elapsed time: 0.862259 msecs"
;"Elapsed time: 7228.72486 msecs"

Performance after (with the patch):

(let [v (vec (range 10000))
      vs (seq v)]
  (time (dotimes [_ 10000]
          (count v)))
  (time (dotimes [_ 10000]
          (count vs))))
;"Elapsed time: 0.967301 msecs"
;"Elapsed time: 0.99391 msecs"

Also with Paul's test case.

Before:

(time (dotimes [_ 10000000] (object-array [1])))
;"Elapsed time: 1668.346997 msecs"
(time (dotimes [_ 10000000] (object-array (rseq [1]))))
;"Elapsed time: 662.820591 msecs"

After:

(time (dotimes [_ 10000000] (object-array [1])))
;"Elapsed time: 757.084577 msecs"
(time (dotimes [_ 10000000] (object-array (rseq [1]))))
;"Elapsed time: 680.602921 msecs"
Show
Tassilo Horn added a comment - This patch makes PersistentVector$ChunkedSeq implement Counted. Performance before: 
(let [v (vec (range 10000))
      vs (seq v)]
  (time (dotimes [_ 10000]
          (count v)))
  (time (dotimes [_ 10000]
          (count vs))))
;"Elapsed time: 0.862259 msecs"
;"Elapsed time: 7228.72486 msecs"
Performance after (with the patch): 
(let [v (vec (range 10000))
      vs (seq v)]
  (time (dotimes [_ 10000]
          (count v)))
  (time (dotimes [_ 10000]
          (count vs))))
;"Elapsed time: 0.967301 msecs"
;"Elapsed time: 0.99391 msecs"
Also with Paul's test case. Before: 
(time (dotimes [_ 10000000] (object-array [1])))
;"Elapsed time: 1668.346997 msecs"
(time (dotimes [_ 10000000] (object-array (rseq [1]))))
;"Elapsed time: 662.820591 msecs"
After: 
(time (dotimes [_ 10000000] (object-array [1])))
;"Elapsed time: 757.084577 msecs"
(time (dotimes [_ 10000000] (object-array (rseq [1]))))
;"Elapsed time: 680.602921 msecs"
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Paul Stadig added a comment -

I don't believe this is Major priority, but I cannot edit the ticket after having created it.

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Paul Stadig added a comment - I don't believe this is Major priority, but I cannot edit the ticket after having created it.

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Dates

  • Created:
    Updated:
    Resolved:
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