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  1. CLJ-1515

range should return something that implements IReduce

    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Completed
    • Affects versions: Release 1.7
    • Fix versions: Release 1.7
    • Labels:
      None
    • Approval:
      Ok
    • Patch:
      Code and Test

      Description

      range should implement IReduce for fast reduction.

      Patch: clj-1515-14.patch - Java range with long optimizations

      Approach: The clj-1515-14 patch revives the unused clojure.lang.Range class. This class is similar in implementation to ChunkedCons. It differs by lazily constructing the first chunk (this is done in the existing impl by using a LazySeq wrapper) and by caching the next reference like other seq impls. The latter is done because range is frequently used in both chunked and unchunked traversal.

      Additionally, 1515-14 contains an optimized version of range (LongRange) for the extremely common case where start, end, and step are all longs. This version uses primitive longs and primitive math and a customized version of ArrayChunk for greater performance.

      The special case of (range) is just handled with (iterate inc' 0) (which was further optimized for reduce in CLJ-1603 Closed ).

      Alternatives:

      • CLJ-1515-deftype3.patch took the approach of using deftype to create a seqable, reducible entity that was not actually a seq. Based on work for CLJ-1603 Closed , it was established that due to historical requirements, this is not viable and the entity returned for range should implement the ISeq and Collection interfaces directly.
      • clj-1515-11.patch uses the approach of a "split" implementation - a LazySeq that has a fast reduce path. This is a minimal patch that provides no perf difference for sequence usage but a moderate improvement for reduce paths. One important difference vs clj-1515-12 is that the fast reduce path is only obtained on the initial range. Once you walk off the head, the performance will be the same as prior (seq perf).

      Performance

      criterium quick-bench with java 1.8.0-b132

      code 1.7.0-master Java clj-1515-14 split clj-1515-11
      (count (range (* 1024 1024))) 63 ms 0 ms 58 ms
      (reduce + (map inc (range (* 1024 1024)))) 50 ms 33 ms 50 ms
      (reduce + (map inc (map inc (range (* 1024 1024))))) 68 ms 52 ms 67 ms
      (count (keep odd? (range (* 1024 1024)))) 73 ms 52 ms 67 ms
      (transduce (comp (map inc) (map inc)) + (range (* 1024 1024))) 46 ms 26 ms 34 ms
      (reduce + 0 (range (* 2048 1024))) 67 ms 19 ms 40 ms
      (reduce + 0 (rest (range (* 2048 1024)))) 67 ms 19 ms 57 ms
      (doall (range 0 31)) 1.04 µs 0.75 µs 1.15 µs
      (doall (range 0 32)) 1.08 µs 0.76 µs 1.18 µs
      (doall (range 0 4096)) 135 µs 96 µs 145 µs
      (into [] (map inc (range 31))) 1.81 µs 1.30 µs 1.88 µs
      (into [] (map inc) (range 31)) 1.71 µs 0.75 µs 1.02 µs
      (into [] (range 128)) 4.82 µs 2.20 µs 3.27 µs
      (doall (range 1/2 1000 1/3)) 1.24 ms 1.24 ms 1.28 µs
      (doall (range 0.5 1000 0.33)) 126 µs 147 µs 151 µs
      (into [] (range 1/2 1000 1/3)) 1.26 ms 1.20 ms 1.26 ms
      (into [] (range 0.5 1000 0.33)) 148 µs 91 µs 130 µs
      (count (filter odd? (take (* 1024 1024) (range)))) 185 ms 167 ms 176 ms
      (transduce (take (* 1024 1024)) + (range)) 67 ms 35 ms 68 ms

      Performance notes:

      • 1515-14 (Java) - significant improvements in virtually all use cases, both seq and reduce. The final two cases with (range) leverage optimizations from CLJ-1603 Closed .
      • 1515-11 (split) - a much smaller patch that gives no seq benefits and smaller reduction benefits. Only the head of the range will receive the perf benefits (see (reduce + 0 (rest (range (* 2048 1024))))).

      Questions
      (range) and supports auto-promotion towards infinity in this patch, which seems to be implied by the doc string but was not actually implemented or tested correctly afaict.

        Attachments

        1. clj-1515.patch
          23 kB
        2. clj-1515-10.patch
          21 kB
        3. clj-1515-11.patch
          6 kB
        4. clj-1515-12.patch
          18 kB
        5. clj-1515-13.patch
          18 kB
        6. clj-1515-14.patch
          18 kB
        7. clj-1515-2.patch
          23 kB
        8. clj-1515-3.patch
          22 kB
        9. clj-1515-4.patch
          22 kB
        10. clj-1515-5.patch
          22 kB
        11. clj-1515-6.patch
          22 kB
        12. clj-1515-7.patch
          22 kB
        13. clj-1515-8.patch
          23 kB
        14. clj-1515-9.patch
          22 kB
        15. CLJ-1515-deftype.patch
          13 kB
        16. CLJ-1515-deftype2.patch
          12 kB
        17. CLJ-1515-deftype3.patch
          12 kB
        18. CLJ-1515-deftype-nostructural-dup.patch
          12 kB
        19. patch.diff
          9 kB
        20. range-patch3.diff
          11 kB
        21. reified-range4.diff
          16 kB

          Activity

            People

            • Assignee:
              Unassigned
              Reporter:
              halgari Timothy Baldridge
            • Votes:
              2 Vote for this issue
              Watchers:
              5 Start watching this issue

              Dates

              • Created:
                Updated:
                Resolved: