I guess this is not connected to our issue.
You're using Clojure's BigInt, which is probably a bit slower than
BigInteger if you know you want it to be big:
user> (class 1N)
clojure.lang.BigInt
Have you tried translating your Java code directly to see if that helps?
On Tue, Jul 2, 2013 at 11:05 AM, Jim - FooBar(); <jimpil1...@gmail.com>wrote:
> I'm really sorry for coming back to this but even after everything we
> learned I'm still not able to get performance equal to java in a simple
> factorial benchmark. I'd like to think that I'm doing all the correct
> things to keep the comparison fair...observe this:
>
> benchmarks.core=> (crit/bench (jf! 50))
> WARNING: Final GC required 2.3432463351555 % of runtime
> Evaluation count : 311580 in 60 samples of 5193 calls.
> Execution time mean : 196.444969 µs
> Execution time std-deviation : 10.637274 µs
> Execution time lower quantile : 194.356268 µs ( 2.5%)
> Execution time upper quantile : 197.042127 µs (97.5%)
> Overhead used : 258.723396 ns
>
> Found 9 outliers in 60 samples (15.0000 %)
> low-severe 2 (3.3333 %)
> low-mild 7 (11.6667 %)
> Variance from outliers : 40.1247 % Variance is moderately inflated by
> outliers nil
>
> now java:
>
> benchmarks.core=> (crit/bench (.factorial ^Benchmarks (Benchmarks.) 50))
> WARNING: Final GC required 2.656271755497413 % of runtime
> Evaluation count : 562260 in 60 samples of 9371 calls.
> Execution time mean : 107.148989 µs
> Execution time std-deviation : 1.650542 µs
> Execution time lower quantile : 106.504235 µs ( 2.5%)
> Execution time upper quantile : 108.934066 µs (97.5%)
> Overhead used : 258.723396 ns
>
> Found 5 outliers in 60 samples (8.3333 %)
> low-severe 1 (1.6667 %)
> low-mild 4 (6.6667 %)
> Variance from outliers : 1.6389 % Variance is slightly inflated by
> outliers
>
> can you spot any differences with this code that would justify needing
> almost twice as much time?
>
> (defn jf! "Calculate factorial of n as fast as Java without overflowing."
> [n]
> (loop [i (int n)
> ret 1N]
> (if (== 1 i) ret
> (recur (dec i) (* ret i)))))
>
> now java:
>
> public BigInteger factorial(final int n){
> BigInteger res = BigInteger.valueOf(1L); //build upresult
> for (int i = n; i > 1; i--)
> res = res.multiply(BigInteger.**valueOf(i));
> return res;
> }
>
> I know this is getting ridiculous but I'm preparing a presentation and
> I was sort of counting on this example...Of course, it goes without
> saying that I'm using unchecked-math and :jvm-opts ^replace[] .
>
>
> am I doing something wrong?
>
> thanks for your time
>
> Jim
>
>
>
> On Fri, 14 Jun 2013 00:11:52 -0700 (PDT)
> Jason Wolfe <ja...@w01fe.com> wrote:
>
> Thanks for your response. I attempted to answer this in my
>> clarification, but our goal is to attack this 'general advice' and
>> make it possible to get the same speed for array handling in
>> natural-seeming Clojure without writing Java. In particular, we want
>> to create macros that make it easy to achieve maximum performance by
>> putting *your code* for manipulating array elements in the middle of
>> an optimized loop, and this can't be done easily at the library level
>> (as far as I can see) by dropping to Java, since in Java your code
>> would always have to be wrapped in a method invocation with
>> corresponding performance implications.
>>
>> Our previous version of this library (developed for Clojure 1.2,
>> IIRC) was able to get within 0-30% or so of raw Java speed while
>> providing a clean Clojure interface, and we're trying to get back to
>> this point with Clojure 1.5 so we can release it as open-source for
>> everyone to use.
>>
>> -Jason
>>
>> On Friday, June 14, 2013 12:04:12 AM UTC-7, Glen Mailer wrote:
>> >
>> > This doesn't really answer your question directly, but is there a
>> > reason you need to keep this in clojure, or are you just aiming to
>> > establish why this is happening?
>> >
>> > My understanding was that for performance critical code the general
>> > advice is to drop down to raw java?
>> >
>> > Glen
>> >
>> >
>>
>>
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