Right! My bad. On Friday, April 26, 2013 2:44:21 PM UTC+2, Ji Zhang wrote: > > Besides, correct me if I'm wrong, the clojure map function returns a lazy > seq, and reduce consumes it, so there's actually only one loop, right? > > On Friday, April 26, 2013 8:23:04 PM UTC+8, Max Penet wrote: >> >> Hi, >> >> In reducer-reduce you iterate twice over the values compared to the java >> version, once in map (just to call .get), then in reduce. >> >> There are other issues probably, but this is one of the obvious ones. >> >> On Friday, April 26, 2013 12:05:33 PM UTC+2, Ji Zhang wrote: >>> >>> Hi, >>> >>> I'm writing map-reduce job with Clojure, yet to find that it seems to be >>> much slower than a Jave job. >>> >>> So I write a simple test case, and upload to gist: >>> https://gist.github.com/jizhang/5466149 >>> >>> At the end of code, there is execution outputs, here are some >>> significant stats: >>> >>> Average time taken by Map tasks: Java 7sec, Clojure 19sec >>> CPU time spent (ms): Java 244,000, Clojure 1,145,440 >>> >>> I'm wondering what slows down the Clojure written map-reduce job. Am I >>> using it wrong, or it's just an inappropriate senario. >>> >>> Any thoughts will be great. Thanks! >>> >>> Jerry >>> >>
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