problems using ghc-6.6.1 (due to fgl-5.4.1)

Simon Peyton-Jones simonpj at
Wed May 9 03:13:25 EDT 2007

Aha!  So the problem is a library change rather than a compiler change.  That's a relief.


| -----Original Message-----
| From: glasgow-haskell-users-bounces at [mailto:glasgow-haskell-users-bounces at] On
| Behalf Of Christian Maeder
| Sent: 08 May 2007 22:33
| To: hets-devel at; GHC Users Mailing List; libraries at
| Subject: problems using ghc-6.6.1 (due to fgl-5.4.1)
| I wrote:
| > Dear Hets- and GHC-Developers,
| > we have a problem using ghc-6.6.1. The created hets binary runs a
| > couple
| > of times slower than the one created using ghc-6.6.
| This problem is gone when I install and use fgl-5.3 (where "hiding
| (indices)" needs to be deleted in Data.Graph.Inductive.Monad.IOArray).
| I strongly suspect the new functions context1l' and context4l' in
| Data.Graph.Inductive.Graph (fgl-5.4.1) to be the reason for our drastic
| slow down.
| In fgl-5.3 the functions fst4 and fth4 have been used instead. A cyclic
| edge (an edge from and to the very same node) was only returned as
| ingoing edge and not as outgoing one. (a design decision documented
| elsewhere).
| I think, the change in fgl-5.4.1 now returns a cyclic edge also as
| outgoing edge (and possibly twice as ingoing one).
| Our application heavily uses in- and outgoing edges that may be cyclic.
| Christian
| P.S. ghc-6.6.1/libraries/fgl/Setup.hs does not compile with ghc-6.6.1
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