I got nothin'. Stare at the bytecode?
On Tue, Jul 2, 2013 at 11:21 AM, Jim - FooBar(); <jimpil1...@gmail.com>wrote:
> with a long counter it needs slightly longer (216 microseconds in
> average instead of 196)!
> any other ideas?
>
>
> On 02/07/13 19:11, Leon Barrett wrote:
>
> Try longs instead of ints? Clojure doesn't support local ints, so you may
> be casting longs to ints a lot.
>
>
> 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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