Marek Karpinski, Alexander Zelikovsky

We study dense instances of several covering problems. An instance of

the set cover problem with $m$ sets is dense if there is $\epsilon>0$

such that any element belongs to at least $\epsilon m$ sets. We show

that the dense set cover problem can be approximated with ...
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Marek Karpinski

We survey recent results on the existence of polynomial time

approximation schemes for some dense instances of NP-hard

optimization problems. We indicate further some inherent limits

for existence of such schemes for some other dense instances of

the optimization problems.

Wenceslas Fernandez de la Vega, Marek Karpinski

TSP(1,2), the Traveling Salesman Problem with distances 1 and 2, is

the problem of finding a tour of minimum length in a complete

weighted graph where each edge has length 1 or 2. Let $d_o$ satisfy

$0<d_o<1/2$. We show that TSP(1,2) has no PTAS on the set ...
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Cristina Bazgan, Wenceslas Fernandez de la Vega, Marek Karpinski

We give a polynomial time approximation scheme (PTAS) for dense

instances of the NEAREST CODEWORD problem.

Cristina Bazgan, Wenceslas Fernandez de la Vega, Marek Karpinski

It is known that large fragments of the class of dense

Minimum Constraint Satisfaction (MIN-CSP) problems do not have

polynomial time approximation schemes (PTASs) contrary to their

Maximum Constraint Satisfaction analogs. In this paper we prove,

somewhat surprisingly, that the minimum satisfaction of dense

instances of kSAT-formulas, ...
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Marek Karpinski

We survey some recent results on the complexity of computing

approximate solutions for instances of the Minimum Bisection problem

and formulate some intriguing and still open questions about the

approximability status of that problem. Some connections to other

optimization problems are also indicated.

Marek Karpinski, Warren Schudy

We design a linear time approximation scheme for the Gale-Berlekamp Switching Game and generalize it to a wider class of dense fragile minimization problems including the Nearest Codeword Problem (NCP) and Unique Games Problem. Further applications include, among other things, finding a constrained form of matrix rigidity and maximum likelihood ... more >>>