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Any randomized algorithm may be interpreted as a randomized choice among deterministic algorithms, and thus as a mixed strategy for Alice. Similarly, a non-random algorithm may be thought of as a pure strategy for Alice. In any two-player zero-sum game, if one player chooses a mixed strategy, then the other player has an optimal pure strategy ...
A randomized algorithm is an algorithm that employs a degree of randomness as part of its logic or procedure. The algorithm typically uses uniformly random bits as an auxiliary input to guide its behavior, in the hope of achieving good performance in the "average case" over all possible choices of random determined by the random bits; thus either the running time, or the output (or both) are ...
Insertion sort applied to a list of n elements, assumed to be all different and initially in random order. On average, half the elements in a list A 1... A j are less than element A j+1, and half are greater. Therefore, the algorithm compares the (j + 1) th element to be inserted on the average with half the already sorted sub-list, so t j = j ...
By applying it to a randomly-permuted graph that contains exactly one clique of size , and applying Yao's principle relating expected and average-case complexity, one can show that any deterministic or randomized algorithm for matroid parity that accesses its matroid only by independence tests needs to make an exponential number of tests.
Average-case analysis requires a notion of an "average" input to an algorithm, which leads to the problem of devising a probability distribution over inputs. Alternatively, a randomized algorithm can be used. The analysis of such algorithms leads to the related notion of an expected complexity. [2]: 28
Therefore, taking the average with respect to the induced distribution on y i, the average-case complexity of f is the same (within polynomial factors) as the worst-case randomized complexity of f. One special case of note is when each random instance y i is distributed uniformly over the entire set of elements in the domain of f that have a ...
This algorithm is much less prone to loss of precision due to catastrophic cancellation, but might not be as efficient because of the division operation inside the loop. For a particularly robust two-pass algorithm for computing the variance, one can first compute and subtract an estimate of the mean, and then use this algorithm on the residuals.
An optimal decision is a decision that leads to at least as good a known or expected outcome as all other available decision options. It is an important concept in decision theory. In order to compare the different decision outcomes, one commonly assigns a utility value to each of them.