Luby’s Restarts

• Luby et al. showed that:

• When the distriution is known, the optimal restart policy is the ﬁxed

cutoff.

• When there is no a priori to the distribution, a universal strategy

minimizes the expected cost.

1, 1, 2, 1, 1, 2, 4, 1, 1, 2, 4, 8, . . .

• Theoretically the universal strategy is within a log factor of the optimal

one, but the convergence is too slowly in practice.

• State-of-the-art SAT solver’s restart:

• Default cutoff value, which is increased linearly

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