[Haskell-cafe] Compiling an extremely large Haskell file (in GHC)

[Stefan Wehr]

Hi,

On Wednesday 29 June 2005 10:05, Duncan Coutts wrote:
> On Tue, 2005-06-28 at 12:11 +0300, Radu Grigore wrote:
> > On 6/27/05, Arjun Guha <GUHAARJU at grinnell.edu> wrote:
> > > It's the all-pairs
> > > shortest paths data for a map of the Hyde Park area of Chicago (no real
> > > reason, really).
> >
> > I wonder: is there really no way to do Floyd-Warshall in Haskell?
>
> Indeed I understand from a colleague who implemented an all-pairs
> shortest paths algorithm in Haskell over the weekend for a map of the
> Hyde Park area of Chicago (no real reason, really!), that it takes about
> 0.1 seconds to execute (if you compile with -O), which is well within
> the 5 second limit...

you can just use dijkstra from the fgl 
(http://www.haskell.org/ghc/docs/latest/html/libraries/fgl/Data.Graph.Inductive.Query.SP.html) 
for the paths you are interested. We used it *a lot* and we didn't have any 
performance problems.

There is really no need to precompute all-pairs shortest path!

Cheers,
  Stefan 

-- 
Stefan Wehr
Web:  http://www.stefanwehr.de
PGP:  Key is available from pgp.mit.edu, ID 0B9F5CE4