[Haskell-cafe] Floyd Warshall performance (again)

[John Lato]

> From: Mathieu Boespflug <mboes at tweag.net>
>
> Dear haskell-cafe,
>
> I implemented the Floyd Warshall algorithm for finding the shortest
> path in a dense graph in Haskell, but noted the performance was
> extremely poor compared to C. Even using mutable unboxed arrays it was
> running about 30 times slower. I rewrote the program several times, to
> arrive at the following definition:
>

My results are basically the same as Max's, but if I change

> #define SIZE 1500
to
> sIZE = 1500

and all references from "SIZE" to "sIZE", something ... changes.  A lot.

MacBook-1:Desktop johnlato$ time ./FW
Allocating ...
Allocating ... done

real	0m0.027s
user	0m0.013s
sys	0m0.014s

I can't figure this out at all.  Can anyone else confirm, or offer a
good explanation?

John