#include <netoptim/network_oracle.hpp>
template<typename Graph, typename Mapping, typename Fn>
NetworkOracle class

Oracle for Parametric Network Problems.

Template parameters
Graph Type of the directed graph
Mapping Type of vertex potential mapping
Fn Type of the constraint function h

This class implements a separation oracle for network feasibility problems. It uses negative cycle detection to check feasibility and generate cutting planes when violations are found.

The oracle maintains:

  • A reference to the graph structure
  • A mapping of vertex potentials (utx)
  • A negative cycle finder for violation detection
  • A function h that evaluates edge constraints

Constructors, destructors, conversion operators

NetworkOracle(const Graph& gra, Mapping& utx, Fn h)
Construct a new network oracle object.
NetworkOracle(const NetworkOracle&) defaulted explicit
Construct a new network oracle object.

Public functions

template<typename Num>
auto update(const Num& gamma) -> void -> auto
Update the oracle with a new parameter value.
template<typename Arr>
auto assess_feas(const Arr& xval) -> std::optional< std::pair< Arr, double > > -> auto
Assess feasibility and generate cutting plane if needed.
template<typename Arr>
auto operator()(const Arr& xvar) -> std::optional< std::pair< Arr, double > > -> auto
Function call operator for cutting plane methods.

Function documentation

template<typename Graph, typename Mapping, typename Fn>
NetworkOracle<Graph, Mapping, Fn>::NetworkOracle(const Graph& gra, Mapping& utx, Fn h)

Construct a new network oracle object.

Parameters
gra in a directed graph (V, E) representing the network
utx in/out vertex potential mapping (updated during operation)
h in function for constraint evaluation and gradient computation

template<typename Graph, typename Mapping, typename Fn> template<typename Num>
auto NetworkOracle<Graph, Mapping, Fn>::update(const Num& gamma) -> void

Update the oracle with a new parameter value.

Parameters
gamma in the new parameter value (best-so-far optimal value)

This method updates the internal constraint function with a new parameter value, typically used in parametric optimization where the constraints depend on a parameter that changes during the algorithm.

template<typename Graph, typename Mapping, typename Fn> template<typename Arr>
auto NetworkOracle<Graph, Mapping, Fn>::assess_feas(const Arr& xval) -> std::optional< std::pair< Arr, double > >

Assess feasibility and generate cutting plane if needed.

Template parameters
Arr Type of the input array/vector
Parameters
xval in input values to be assessed for feasibility
Returns std::optional<std::pair<Arr, double>> Empty if feasible, otherwise a pair containing gradient and function value for cutting plane

This is the main oracle method that checks if the current point xval is feasible with respect to the network constraints. If infeasible, it returns a cutting plane (gradient and function value) that separates the infeasible point from the feasible region.

The method works by:

  1. Computing edge weights using the constraint function
  2. Searching for negative cycles using these weights
  3. If found, computing the gradient and function value for the cut
  4. Returning the cutting plane or empty if feasible

template<typename Graph, typename Mapping, typename Fn> template<typename Arr>
auto NetworkOracle<Graph, Mapping, Fn>::operator()(const Arr& xvar) -> std::optional< std::pair< Arr, double > >

Function call operator for cutting plane methods.

Template parameters
Arr Type of the input array/vector
Parameters
xvar in input variables to be assessed
Returns std::optional<std::pair<Arr, double>> Same as assess_feas

This operator makes the oracle callable, which is convenient for use with cutting plane algorithms. It simply forwards to the assess_feas method.