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Fault-Tolerant Shortest Paths - Beyond the Uniform Failure Model
The overwhelming majority of survivable (fault-tolerant) network design
models assume a uniform scenario set. Such a scenario set assumes that every
subset of the network resources (edges or vertices) of a given cardinality
comprises a scenario. While this approach yields problems with clean
combinatorial structure and good algorithms, it often fails to capture the true
nature of the scenario set coming from applications.
One natural refinement of the uniform model is obtained by partitioning the
set of resources into faulty and secure resources. The scenario set contains
every subset of at most faulty resources. This work studies the
Fault-Tolerant Path (FTP) problem, the counterpart of the Shortest Path problem
in this failure model. We present complexity results alongside exact and
approximation algorithms for FTP. We emphasize the vast increase in the
complexity of the problem with respect to its uniform analogue, the
Edge-Disjoint Paths problem
Compactly generating all satisfying truth assignments of a Horn formula
As instance of an overarching principle of exclusion an algorithm is
presented that compactly (thus not one by one) generates all models of a Horn
formula. The principle of exclusion can be adapted to generate only the models
of weight . We compare and contrast it with constraint programming,
integer programming, and binary decision diagrams.Comment: Considerably improves upon the readibility of the previous versio
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