calibration_cpp         Calibrating the balancing factors
cpp_found_openmp        Function to check availability of OPENMP to run
                        in parallel. If openmp is found, this function
                        returns TRUE
distance_test           distance_test
flows_london            flows_london
flows_test              flows_test
london_msoa             london_msoa
run_model               Running doubly constrained model
run_model_cpp           Run model
run_model_single        Running a singly constrained model
simulation              Running a whole simulation of a doubly
                        constrained gravity model
