Computational time for sensor selection as a function of (a) the fraction of observed nodes f and (b) the observation horizon N. The various curves correspond to Method 1 (■), Method 2 (●), Method 3 (▴), and Method 4 (▾), applied to the GRI-Mech 3.0 network. Results are averaged over 10 random initial guesses for the selected sensors, using the IRK model and h = 10−13, for N = 200 in panel a and f = 0.5 in panel b.