I was doing some microbenchmarking earlier, and I noticed some very very weird anomalies. If anyone could shed some light on what's going on that would be awesome. (I'm using the latest SVN, and have verified this on a totally clean repl).
Simplified as much as possible, the heart of what I observed is: user> (prn (time (loop [i (int 0)] (if (< i (int 30000000)) (recur (inc i)) i)))) "Elapsed time: 4247.477 msecs" 30000000 nil user> (time (loop [i (int 0)] (if (< i (int 30000000)) (recur (inc i)) i))) "Elapsed time: 128.37 msecs" 30000000 Weird, right? The prn is *outside* the loop, and yet it still affects the timing somehow. Maybe this is something specific to printing? Nope: user> (first (time (loop [i (int 0)] (if (< i (int 30000000)) (recur (inc i)) [i])))) "Elapsed time: 4264.847 msecs" 30000000 user> (time (loop [i (int 0)] (if (< i (int 30000000)) (recur (inc i)) [i]))) "Elapsed time: 130.099 msecs" [30000000] But, some other expressions around the "time" don't affect it in the same way: user> (when (time (loop [i (int 0)] (if (< i (int 30000000)) (recur (inc i)) [i]))) 12) "Elapsed time: 130.236 msecs" 12 In case you were wondering, this has nothing to do with the "time" macro. user> (first (loop [i (int 0)] (if (< i (int 30000000)) (recur (inc i)) [i]))) ; ... 4 seconds pass on my stopwatch ... 30000000 And the slowness is by a multiplicative, not additive factor: user> (first (time (loop [i (int 0)] (if (< i (int 60000000)) (recur (inc i)) [i])))) "Elapsed time: 8576.649 msecs" 60000000 user> (time (loop [i (int 0)] (if (< i (int 60000000)) (recur (inc i)) [i]))) "Elapsed time: 250.407 msecs" [60000000] I'm at a total loss for what's going on. Anyway, I'll stop here for now in case I'm missing something stupid or obvious. Thanks for your help! Jason --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
