The Scala code is using immutable sets.
On Wednesday, October 23, 2013, Timothy Baldridge wrote:
> From what I can tell, Clojure uses persistent hash sets inside of set.
> This can be fixed by replacing set with (into #{} data). Into uses
> transients internally and should be much faster.
>
> I don't know Scala, but from I can tell, Scala is using mutable
> collections. I think the combination of these two things (immutable
> collections plus lack of transients) could be causing some performance
> impact. I wouldn't expect it to be 1000x but it's a starting place.
>
> Timothy
>
>
> On Wed, Oct 23, 2013 at 6:36 AM, Paul Butcher
> <p...@paulbutcher.com<javascript:_e({}, 'cvml', 'p...@paulbutcher.com');>
> > wrote:
>
>> On 23 Oct 2013, at 13:18, Timothy Baldridge
>> <tbaldri...@gmail.com<javascript:_e({}, 'cvml', 'tbaldri...@gmail.com');>>
>> wrote:
>>
>> Great! you have a profiler, use that. Find the hotspots, use YourKit to
>> find where the .cons is being called from, find things to optimize, and go
>> from there. This is exactly the same process I would use any optimizations
>> I attempted.
>>
>>
>> I fear I may have failed to convey the question I'm trying to answer.
>>
>> I'm sure that I could create a faster solution in Clojure - that's not
>> the question I'm trying to answer though.
>>
>> What I'm trying to answer is why the *exact same* algorithm implemented
>> in Scala is 1000x faster.
>>
>> As far as I know, the Scala version of the algorithm creates exactly as
>> many sets and performs exactly as many set operations as the Clojure does.
>> But the Clojure version is 1000x slower. That strikes me as very strange
>> and worth getting to the bottom of?
>>
>> I have, of course, looked at the result of the profiler. And what it
>> seems to be saying is that set operations in Clojure are ruinously slow.
>> I'm not sure that I believe that though - I can't think of any reason why
>> Clojure's sets should be 1000x slower than Scala's? So I'm asking for the
>> help of this list.
>>
>> Of course, I can't rule out the possibility that I've failed to convert
>> the Scala version to Clojure and they're actually implementing very
>> different algorithms - but I've had several people look at the
>> implementations and confirm that they appear to be the same. Nevertheless,
>> if there is a problem there, I'd also be interested to find it as I'm sure
>> that it will teach me something.
>>
>> --
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>>
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>
>
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