Edmund Ihler

We show that a fully polynomial time approximation scheme given

for an optimization problem can always be simply modified to a

polynomial time algorithm solving the problem optimally if the

computation model is the deterministic Turing Machine or the

logarithmic cost RAM and ...
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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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Chandra Chekuri, Sanjeev Khanna

We present the first approximation schemes for minimizing weighted flow time

on a single machine with preemption. Our first result is an algorithm that

computes a $(1+\eps)$-approximate solution for any instance of weighted flow

time in $O(n^{O(\ln W \ln P/\eps^3)})$ time; here $P$ is the ratio ...
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Wenceslas Fernandez de la Vega, Marek Karpinski

We prove that MAX-3SAT can be approximated in polynomial time

within a factor 9/8 on random instances.

Wenceslas Fernandez de la Vega, Marek Karpinski

We prove existence of approximation schemes for instances of MAX-CUT with $\Omega(\frac{n^2}{\Delta})$ edges which work in $2^{O^\thicksim(\frac{\Delta}{\varepsilon^2})}n^{O(1)}$ time. This entails in particular existence of quasi-polynomial approximation schemes (QPTASs) for mildly sparse instances of MAX-CUT with $\Omega(\frac{n^2}{\operatorname{polylog} n})$ edges. The result depends on new sampling method for smoothed linear programs that ... more >>>

Claire Kenyon-Mathieu, Warren Schudy

Suppose you ran a chess tournament, everybody played everybody, and you wanted to use the results to rank everybody. Unless you were really lucky, the results would not be acyclic, so you could not just sort the players by who beat whom. A natural objective is to find a ranking ... more >>>

Wenceslas Fernandez de la Vega, Marek Karpinski

We construct the first constant time value approximation schemes (CTASs) for Metric and Quasi-Metric MAX-rCSP problems for any $r \ge 2$ in a preprocessed metric model of computation, improving over the previous results of [FKKV05] proven for the general core-dense MAX-rCSP problems. They entail also the first sublinear approximation schemes ... more >>>