[Help-glpk] shortest path

[Rik Fieten]

hello all,
I'd like to pose a problem: I have a fairly huge model (600 nodes) and I 
would like to find the shortest path from all nodes to all nodes. So 
this wil probably give around 600*600 shortest distances. Because I'm 
quite new to mathprog and glpk, I took an example of the glpk package 
(spp.mod). This example works fine, but it calculates only one shortest 
path (from one (preset) node to another (preset) node). Can I somehow 
introduce somewhere a kind of "for-loop" (I guess) to solve this 
problem? Or do you have another solution to my problem? I tried to write 
all different files, with the same model, but every time a different 
source (start node) and sink (end node), but it is quite time consuming 
to read every time this enormous model.
Thanks,
Rik