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Balancing poset extensions. (English) Zbl 0561.06004
From the author’s abstract: Theorem: Any finite partially ordered set P, which is not totally ordered, contains a pair of elements x and y such that the proportion of linear extensions of P in which x lies below y is between 3/11 and 8/11. A consequence is that the information theoretic lower bound for sorting under partial information is tight up to a multiplicative constant. Precisely: if X is a totally ordered set about which we are given some partial information, and if e(X) is the number of total orderings of X compatible with this information, then it is possible to sort X using no more than C log$${}_ 2e(X)$$ comparisons where C is approximately 2.17.
Reviewer: T.Ohkuma

##### MSC:
 06A06 Partial orders, general 68P10 Searching and sorting 06A05 Total orders 05A20 Combinatorial inequalities
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##### References:
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