Hi there,

I have a question about the following example: FICO Xpress Examples Repository: Ground transport. I have extended the model and now I'm looking for an algorithm to solve the model. This problem is a minimum cost (network) flow model and Mosel Xpress uses the dual simplex LP relaxation to solve. I'm thinking about "a tailored procedure" such as the (primal) network simplex algorithm, a specialized version of the classical simplex algorithm. Is this a solid choice or does Xpress solve the model in such a way already? Thank you in advance!

Kind regards

Hi Tom,

Xpress will by default use the dual simplex algorithm for solving an LP like this. It does offer a network simplex method, but you have to explicitly tell Xpress to try it. What it will then do is identify any network structure in the problem and apply the network simplex method to this part. If the network simplex can not solve the full problem, either primal or dual simplex will be used to finish the solve.

In Mosel you tell Xpress to try the network simplex method by providing the XPRS_NET option to the minimize/maximize call, as in:

minimize(XPRS_NET, Cost)

I should point out that the default dual simplex method can often solve a network problem more efficiently than the network simplex method, due to the more advanced pivot selection schemes available in dual simplex.

Best Regards,

Michael