[Lemon-user] User Data Structures

[Alpar Juttner]

Hi,

> I am new to Lemon. I would like to know if there is a way to access
> user data structures from within an algorithm.

You have access to anything for the source code is in your hand!
The implementation of most of the algorithms are quite easy to
understand and to modify once you know how the algorithm works.

>  I have a max flow problem with a side constraint which I intend to
> solve using Network Simplex method.

What do you actually mean by side constraint?

For example, you may want to solve the minimum cost flow problem with
and additional w*x <= B type constraint (i.e. if you want to keep the
weighted some of the flow values below a limit B).

Unfortunately, the Network simplex algorithm cannot handle this problem
for it heavily rely on the special structure of the basic solutions of
the network flow problem.

Instead you should either
      * formulate the whole problem as an LP and solve it with an LP
        solver or
      * use a Lagrange relaxation technique for eliminating the
        additional constraint.

The first choice is the easiest. The second one needs some programming,
but may be more efficient.

Regards,
Alpar