On Sunday, February 3, 2013 1:07:41 AM UTC-5, puzzler wrote:
>
> I just went through the process of converting my map-based program over to
> records, hoping it would improve speed. Much to my dismay, it actually
> slowed my program down substantially. With some profiling, I discovered
> that one possible explanation is that (at least in RC4) hashing of records
> is about 60x slower than their map-based counterpart.
>
> (defrecord A [x y])
> => (time (dotimes [n 10000000] (hash {:x "a" :y 3})))
> "Elapsed time: 90.631072 msecs"
> => (time (dotimes [n 10000000] (hash (A. "a" 3))))
> "Elapsed time: 5549.788311 msecs"
>
> Any thoughts about why this is the case?
>
There was a change for 1.5 to cache hasheq for maps
https://github.com/clojure/clojure/commit/d77489d3ce912c177fe288a6f399a5c1da6683db
but the same is not done for defrecords. That is why maps are so much
faster than records.
Paul
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