Fixed-parameter algorithms for DAG Partitioning. van Bevern, R., Bredereck, R., Chopin, M., Hartung, S., Hüffner, F., Nichterlein, A., & Suchý, O. Discrete Applied Mathematics, 220:134–160, 2017.
Fixed-parameter algorithms for DAG Partitioning [link]Preprint  Fixed-parameter algorithms for DAG Partitioning [link]Code  doi  abstract   bibtex   
Abstract Finding the origin of short phrases propagating through the web has been formalized by Leskovec et al. (2009) as \DAG\ Partitioning: given an arc-weighted directed acyclic graph on n  vertices and m  arcs, delete arcs with total weight at most  k such that each resulting weakly-connected component contains exactly one sink—a vertex without outgoing arcs. \DAG\ Partitioning is NP-hard. We show an algorithm to solve \DAG\ Partitioning in O ( 2 k ⋅ ( n + m ) )  time, that is, in linear time for fixed  k . We complement it with linear-time executable data reduction rules. Our experiments show that, in combination, they can optimally solve \DAG\ Partitioning on simulated citation networks within five minutes for k ≤ 190 and m being  10 7 and larger. We use our obtained optimal solutions to evaluate the solution quality of Leskovec et al.’s heuristic. We show that Leskovec et al.’s heuristic works optimally on trees and generalize this result by showing that \DAG\ Partitioning is solvable in 2 O ( t 2 ) ⋅ n time if a width- t tree decomposition of the input graph is given. Thus, we improve an algorithm and answer an open question of Alamdari and Mehrabian (2012). We complement our algorithms by lower bounds on the running time of exact algorithms and on the effectivity of data reduction.
@article{BBC+17,
  title =	 "Fixed-parameter algorithms for {DAG} Partitioning",
  journal =	 "Discrete Applied Mathematics",
  volume =	 220,
  pages =	 "134--160",
  year =	 2017,
  issn =	 "0166-218X",
  doi =		 "10.1016/j.dam.2016.12.002",
  author =	 "René van Bevern and Robert Bredereck and Morgan
                  Chopin and Sepp Hartung and Falk Hüffner and André
                  Nichterlein and Ondřej Suchý",
  keywords =	 "NP-hard problem",
  keywords =	 "Graph algorithms",
  keywords =	 "Polynomial-time data reduction",
  keywords =	 "Multiway cut",
  keywords =	 "Linear-time algorithms",
  keywords =	 "Algorithm engineering",
  keywords =	 "Evaluating heuristics ",
  abstract =	 "Abstract Finding the origin of short phrases
                  propagating through the web has been formalized by
                  Leskovec et al. (2009) as \{DAG\} Partitioning:
                  given an arc-weighted directed acyclic graph on n
                   vertices and m  arcs, delete arcs with total weight
                  at most  k such that each resulting weakly-connected
                  component contains exactly one sink—a vertex without
                  outgoing arcs. \{DAG\} Partitioning is NP-hard. We
                  show an algorithm to solve \{DAG\} Partitioning in O
                  ( 2 k ⋅ ( n + m ) )  time, that is, in linear time
                  for fixed  k . We complement it with linear-time
                  executable data reduction rules. Our experiments
                  show that, in combination, they can optimally solve
                  \{DAG\} Partitioning on simulated citation networks
                  within five minutes for k ≤ 190 and m being  10 7
                  and larger. We use our obtained optimal solutions to
                  evaluate the solution quality of Leskovec et al.’s
                  heuristic. We show that Leskovec et al.’s heuristic
                  works optimally on trees and generalize this result
                  by showing that \{DAG\} Partitioning is solvable in
                  2 O ( t 2 ) ⋅ n time if a width- t tree
                  decomposition of the input graph is given. Thus, we
                  improve an algorithm and answer an open question of
                  Alamdari and Mehrabian (2012). We complement our
                  algorithms by lower bounds on the running time of
                  exact algorithms and on the effectivity of data
                  reduction. ",
  url_Preprint = {https://arxiv.org/abs/1611.08809},
  url_Code =	 {https://gitlab.com/rvb/dagpart/}
}

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