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On random orderings of variables for parity ordered binary decision diagrams

✍ Scribed by Petr Savický


Publisher
John Wiley and Sons
Year
2000
Tongue
English
Weight
93 KB
Volume
16
Category
Article
ISSN
1042-9832

No coin nor oath required. For personal study only.

✦ Synopsis


Ordered binary decision diagrams (OBDDs) are a model for representing

Boolean functions. There is also a more powerful variant called parity OBDDs. The size of the representation of a given function depends in both these models on the chosen ordering of the variables. It is known that there are functions such that almost all orderings of their variables yield an OBDD of polynomial size, but there are also some exceptional orderings, for which the size is exponential. We prove that for parity OBDDs, the size for a random ordering and the size for the worst ordering are polynomially related. More exactly, for every ε > 0 there is a number c > 0 such that the following holds. If a Boolean function f of n variables is such that a random ordering of the variables yields a parity OBDD for f of size at most s with probability at least ε, where s ≥ n, then every ordering of the variables yields a parity OBDD for f of size at most s c .


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