On Sat, Feb 19, 2011 at 4:38 AM, Johan Tibell
Hi all,
I am delighted to announce the release of preview versions of two new packages:
unordered-containers 0.1 Efficient hashing-based container types. http://hackage.haskell.org/package/unordered-containers
hashable 1.1 Efficient hashing of common types. http://hackage.haskell.org/package/hashable
These packages address a need for faster container types in Haskell, especially for string types like ByteString and Text. The package achieves better performance by using hashing and a Patricia trie (also known as a radix tree), instead of a balanced tree, in its implementation.
The provided HashMap type is three times faster than Data.Map for lookups and twice as fast for inserts, for all key types I've tried, including ByteString, String, and Int.
I'm calling this a preview release, even though the code hash been well tested both for correctness and performance, as the API is quite basic and doesn't provide a HashSet type yet. One thing you'll notice is that the API is split into a value-strict and a value-lazy version, making it easier to use in a strict setting.
If you want to contribute, please get copies of the source trees from here:
* git clone https://github.com/tibbe/unordered-containers.git * git clone https://github.com/tibbe/hashable.git
Alternatively, just fork the projects on GitHub:
As I mentioned in my talk on hashing-based containers earlier this week, I'm working on an even faster version, based on hash-array mapped tries, but it won't be ready until GHC 7.2.
Johan
What about making Hashable subclass of Eq class Eq a => Hashable a where I think it's is obvious from Hasable class properties that some kind of equality is needed and I think it will reduce type class constraints in actual hash table implementation in unordered-containers package. Also I think that value of hash functions is obviously a Monoid and it will be convenient to have Monoid instance newtype Hash = Hash Int instance Monoid Hash where mempty = Hash 0 Hash a `mappend` Hash b = Hash (a `combine` b) class Eq a => Hashable a where hash :: a -> Hash hashWithSalt :: Hash -> a -> Hash hashWithSalt salt x = salt `mappend` hash x -- Victor Nazarov