[Lemon-user] number of STATE_TREE vars at end of network simplex

[Matthew Galati]

Hi. I am trying to form a basis to hand a standard LP simplex solver (dual
simplex) after running LEMON's network simplex. From my understanding,
network simplex forms the basis as a spanning tree, which will have m-1
entries (where m = the number of rows = the number of nodes in network). And
the last element of the basis would normally come from a basic "artificial
variable" - which seems it can be found by looking for the row with _pi[i] =
0.

I am running against a Dimacs format file. Net simplex solves the problem
fine, but at the end, I print out the number of arcs with STATE_TREE (basic)
and it is not what I had expected. There are 256 nodes in the network, but
only 252 links that are set to basic.

Am I interpreting the basis incorrectly? Or might there be a bug?

Let me know if you want the dimacs file to repeat the issue I am seeing.

Thanks,
Matt
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