On the Parameterized Intractability of CLOSEST SUBSTRINGsize and Related Problems

  • Authors:
  • Michael R. Fellows;Jens Gramm;Rolf Niedermeier

  • Affiliations:
  • -;-;-

  • Venue:
  • STACS '02 Proceedings of the 19th Annual Symposium on Theoretical Aspects of Computer Science
  • Year:
  • 2002

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Abstract

We show that CLOSEST SUBSTRING, one of the most important problems in the field of biological sequence analysis, is W[1]-hard with respect to the number k of input strings (even over a binary alphabet). This problem is therefore unlikely to be solvable in time O(f(k)nc) for any function f and constant c independent of k -- effectively, the problem can be expected to be intractable, in any practical sense, for k 驴 3. Our result supports the intuition that CLOSEST SUBSTRING is computationally much harder than the special case of CLOSEST STRING, although both problems are NP-complete and both possess polynomial time approximation schemes. We also prove W[1]-hardness for other parameterizations in the case of unbounded alphabet size. Our main W[1]- hardness result generalizes to CONSENSUS PATTERNS, a problem of similar significance in computational biology.