Data.HashTable performance

Don Stewart dons00 at
Wed Apr 6 05:37:20 CEST 2011

Actually, Data.HashTable got some good attention recently from Simon
Marlow (modifying the GC), and Johan Tibell and others looking at
containers performance in general:

Certainly, being in IO limits the utility of a hashtable library
(since it isn't thread safe or persistent by default), but that
doesn't mean the structure gets neglected.

Johan, what's your thoughts on the status?

-- Don

On Tue, Apr 5, 2011 at 8:31 PM, Thomas DuBuisson
<thomas.dubuisson at> wrote:
> The hashtable in base is used very little by the Haskell community,
> partly due to it being IO heavy and partly a result of its known
> performance issues that no one seems motivated to address.  I suggest
> you look at the unordered-containers package which is rather new but
> positioned to become the de facto standard.  Currently, many people
> needing a key/value mapping lean on Data.Map from the containers
> package (a balanced tree).
> Cheers,
> Thomas
> On Tue, Apr 5, 2011 at 5:53 PM, Frank Kuehnel <vincef13 at> wrote:
>> Out of curiosity, I've tested a few Hashtable implementations:
>> Are there any clues why Haskell's Data.HashTable doesn't perform better?
>> I would have expected a similar performance like with F# on the Mono 2.0
>> platform.
>> Thanks,
>> Frank
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