Which is out of date.

On Thu, Apr 25, 2013 at 12:47 PM, Alice <dofflt...@gmail.com> wrote:

> Found this blog post written by fogus:
>
> "To provide this level of flexibility Clojure establishes a level of
> indirection. Specifically, all function lookups through a Var occur,
> at the lowest level, through an atomic volatile. This happens every
> time that a function bound using the def/defn special forms is called.
> This indirection is not amenable to HotSpot optimizations."
>
>
> http://blog.fogus.me/2011/10/14/why-clojure-doesnt-need-invokedynamic-but-it-might-be-nice/
>
> On Apr 25, 10:19 pm, Alice <dofflt...@gmail.com> wrote:
> > I create many small methods in java without worrying about the
> > performance since it's usually the target of inline optimization. For
> > example,
> >
> > public class Foo {
> >   public static long inc(long l) {
> >     return ++l;
> >   }
> >
> >   public static long f1() {
> >     long l = 0;
> >     for (int i=0; i < 1000000000; i++) {
> >       l++;
> >     }
> >     return l;
> >   }
> >
> >   public static long f2() {
> >     long l = 0;
> >     for (int i=0; i < 1000000000; i++) {
> >       l = inc(l);
> >     }
> >     return l;
> >   }
> >
> > }
> >
> > (time (Foo/f1))
> > (time (Foo/f1))
> > (time (Foo/f1))
> > (time (Foo/f2))
> > (time (Foo/f2))
> > (time (Foo/f2))
> >
> > "Elapsed time: 23.309532 msecs"
> > "Elapsed time: 23.333039 msecs"
> > "Elapsed time: 21.714753 msecs"
> > "Elapsed time: 22.943366 msecs"
> > "Elapsed time: 21.612783 msecs"
> > "Elapsed time: 21.71376 msecs"
> >
> > But clojure funtions seem to be never get inlined.
> >
> > (def obj (Object.))
> >
> > (defn getObj [] obj)
> >
> > (defn f1 [] obj)
> > (defn f2 [] (getObj))
> >
> > (time (dotimes [n 100000000] (f1)))
> > (time (dotimes [n 100000000] (f1)))
> > (time (dotimes [n 100000000] (f1)))
> > (time (dotimes [n 100000000] (f2)))
> > (time (dotimes [n 100000000] (f2)))
> > (time (dotimes [n 100000000] (f2)))
> >
> > "Elapsed time: 67.758744 msecs"
> > "Elapsed time: 68.555306 msecs"
> > "Elapsed time: 68.725147 msecs"
> > "Elapsed time: 104.810459 msecs"
> > "Elapsed time: 103.273618 msecs"
> > "Elapsed time: 103.374595 msecs"
>
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