Did you run it enough times to fully warm up the JVM? On Fri, Oct 10, 2014 at 4:21 PM, Michael Blume <blume.m...@gmail.com> wrote:
> https://github.com/MichaelBlume/eval-speed > eval-speed.core=> (time-fn read-to-maps) > "Elapsed time: 5551.011069 msecs" > nil > eval-speed.core=> (time-fn read-to-maps-fn) > "Elapsed time: 5587.256991 msecs" > nil > eval-speed.core=> (time-fn read-to-maps-partial) > "Elapsed time: 5606.649172 msecs" > nil > eval-speed.core=> (time-fn read-to-maps-eval) > "Elapsed time: 2627.521592 msecs" > nil > Ben, I'd still like to understand exactly what work the CPU is doing in the > uneval'd version that it's skipping in the eval'd version. It seems like in > the generated bytecode there's going to be *some* concept of iterating > through the row in either case, if only as part of the destructuring > process. > On Friday, October 10, 2014 1:07:08 PM UTC-7, Ben wrote: >> >> I believe it's because the `mapper` function is just creating and >> returning a map literal. The "mapper" function in the evaled version is >> something like this: >> >> user> (def names '[n1 n2 n3 n4]) >> #'user/names >> user> (def headers '[h1 h2 h3 h4]) >> #'user/headers >> user> `(fn [[~@names]] ~(zipmap headers names)) >> (clojure.core/fn [[n1 n2 n3 n4]] {h4 n4, h3 n3, h2 n2, h1 n1}) ;; just a >> map literal, whose keys are already known. >> >> Whereas in the first version, zipmap has to be called, iterating over >> headers and names each time. >> >> On Fri, Oct 10, 2014 at 1:04 PM, Sean Corfield <se...@corfield.org >> <javascript:>> wrote: >> >>> It may be more to do with the difference between `for` and `map`. How do >>> these versions compare in your benchmark: >>> >>> (defn read-to-maps-partial [rows] >>> (let [headers (->> >>> rows >>> first >>> (take-while (complement #{""})) >>> (map keyword))] >>> (map (partial zipmap headers) (rest rows)))) >>> >>> (defn read-to-maps-fn [rows] >>> (let [headers (->> >>> rows >>> first >>> (take-while (complement #{""})) >>> (map keyword)) >>> mapper (fn [row] (zipmap headers row))] >>> (map mapper (rest rows)))) >>> >>> Sean >>> >>> On Oct 10, 2014, at 11:42 AM, Michael Blume <blume...@gmail.com >>> <javascript:>> wrote: >>> > So I'm reading a bunch of rows from a huge csv file and marshalling >>> those rows into maps using the first row as keys. I wrote the function two >>> ways: https://gist.github.com/MichaelBlume/c67d22df0ff9c225d956 and the >>> version with eval is twice as fast and I'm kind of curious about why. >>> Presumably the eval'd function still implicitly contains a list of keys, >>> it's still implicitly treating each row as a seq and walking it, so I'm >>> wondering what the seq-destructuring and the map literal are doing under >>> the hood that's faster. >>> >>> >> >> >> -- >> Ben Wolfson >> "Human kind has used its intelligence to vary the flavour of drinks, which >> may be sweet, aromatic, fermented or spirit-based. ... Family and social >> life also offer numerous other occasions to consume drinks for pleasure." >> [Larousse, "Drink" entry] >> >> > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with your > first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
