runtimes to find the optimal COF x over these random initializing sets of COFs. (Each individual search efficiency trace is shown in Fig. .) While there is significant variance in the runtimes (standard deviations: 63 hr for SFBO, 25 hr for MFBO), the distribution of the runtime of MFBO is shifted far to the left of that of SFBO (means: 261 hr for SFBO, 58 hr for MFBO).