On 9 March 2010 06:57, Jonathan Shore <jonathan.sh...@gmail.com> wrote:
> the second because maps clearly are not "near the metal"
maps are actually very very efficiently implemented. Small maps are
especially efficient as they are implemented as array maps.
user=> (type {:a 1, :b 2})
clojure.lang.PersistentArrayMap
At ten entries you get hash-maps, and these are still great.
user=> (type {:a 1, :b 2, :c 3, :d 4, :e 5, :f 6, :g 7, :h 8, :i 9, :j 10})
clojure.lang.PersistentHashMap
You can also define structs which gives a slight optimization. I have
yet to find a case where I would prefer a struct over a map though.
You also have the option of writing a Java class. Clojure allows
pretty much any optimization you can throw at a problem. All the tools
are there if you really need to crank out the cpu cycles or memory
bytes. But the provided data structures are really really good.
I would encourage you to embrace the Clojure data structures and use
them as much as possible with as little ceremony as possible, and only
look to optimize when you find it necessary to meet your
performance/memory goals.
For some really specific information on optimizing array access you
might be interested in this article
http://clj-me.cgrand.net/category/interop/
where Christophe Grand explores the effects of type hinting on arrays
and multi-dimensional arrays. The details can be a bit overwhelming so
I only recommend it if you are really keen on diving deep!
You might also be interested in this library by Konrad (I've not used
it but KH libraries are usually great!)
http://code.google.com/p/clj-multiarray/
Regards,
Tim.
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