Algorithmic aspects of convexity . Santosh Vempala ’ s lecture
نویسنده
چکیده
We assume that the convex set K is presented by an oracle. We shall consider two kinds of oracles: • Separation Oracle: we ask if a point x is in K. If x ∈ K, the oracle answers ”yes”. If x / ∈ K the oracle returns a half-space H such that K ⊂ H and x / ∈ K. In addition, we are given two numbers r,R ∈ R such that there exists a point x0 (unknown) satisfying x0 + rBn ⊂ K ⊂ RBn. • Membership Oracle: we ask if a point x is in K. If x ∈ K, the oracle answers ”yes”. If x / ∈ K, the oracle answers ”no”. Here in addition to the oracle we need an initial given point x0 ∈ K, and two radius r,R ∈ R so that x0 + rBn ⊂ K ⊂ RBn.
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