2010/10/18 Dmitriy S. <samborsk...@yahoo.com>:
> On Oct 18, 3:07 pm, Jürgen Hötzel <juer...@hoetzel.info> wrote:
>> > (defn sum [arr]
>> > (loop [i (int 0) s (int 0)]
>> > (if (= i *N*) s
>>
>> ^^^^^^^^^^^
>>
>> You still doing non-primitive ops here.
>
> Indeed, I overlooked that.
> But this was not the main cause of the trouble.
>
>> Also Check for areduce:
>>
>> (defn sum [^ints arr]
>> (areduce arr i ret (int 0)
>> (unchecked-add-int ret (aget arr i))))
>
> This code works at the top speed.
> (the time with Clojure-1.2 now is ~17 msec, same as for Java, and
> with Clojure-1.3-alpha it's 67 msec)
>
> By comparing my code with areduce macro I've found
> what was the problem -- it's a '=' operator, which I used
> instead of '>='.
>
> Therefore this version of areduce is ~10 times slower
> (in spite of being equivalent logically with the original one):
>
> (defmacro areduce-slow
> "Reduces an expression across an array a, using an index named idx,
> and return value named ret, initialized to init, setting ret to the
> evaluation of expr at each step, returning ret."
> {:added "1.0"}
> [a idx ret init expr]
> `(let [a# ~a]
> (loop [~idx (int 0) ~ret ~init]
> (if (= ~idx (alength a#)) ;; '=' instead of '>=' (but original
Note the difference between "=" and "==", "=" will result in a cast to
the wrapped types for it's arguments.
Jürgen
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