Proposal: Further performance improvements of Data.Map

[Milan Straka]

Hi,

see http://hackage.haskell.org/trac/ghc/ticket/4311.

The following text is the description of ticket 4311:

This proposal depends on #4277 and #4278.

This proposal further improves the performance of Data.Map. It consists of four patches:

   1. improvements to union and difference implementation( by eliminating high-order function)
   2. improvements to balance function which is used by nearly all methods modifying a map (making one monolithic function which allows perform only one pattern-match on the tree nodes)
   3. correction of the test (the Arbitrary instance could generate unbalanced trees, which the patch 2. discovered)
   4. added benchmark of union, difference and intersection methods

On i386 Intel Core2 and GHC 6.12.1, the improvements are

alter                       5.61
delete                      10.80
difference                  20.33
insert                      8.09
intersection                7.69
union                       21.74
update                      7.96

The repository of the containers package with these patches (and also several others) is at  http://fox.auryn.cz/darcs/containers/.

The patches are also attached.