Comparison of durations for MCMC and VEM analyses in terms of parcel size, each dot coding for a different parcel. (a): differential timing Δt = t _MCMC −t _VEM. (b): gain factor G_f = t _MCMC /t _VEM of VEM compared to MCMC, the horizontal line indicates a gain factor of one (G_f = 1). Circles are -colored for parcels estimated as activated, ie max{(μ̂ _{1 m} )_{1≤ m ≤ M} } ≥ 8 and -colored otherwise.