Lesson plan

Generic-case complexity

Generic-case complexity is a subfield of computational complexity theory that studies the complexity of computational problems on "most inputs". Generic-case complexity is a way of measuring the complexity of a computational problem by neglecting a small set of unrepresentative inputs and considering worst-case complexity on the rest. Small is defined in terms of asymptotic density. The apparent efficacy of generic case complexity is because for a wide variety of concrete computational problems, the most difficult instances seem to be rare. Typical instances are relatively easy. This approach to complexity originated in combinatorial group theory, which has a computational tradition going back to the beginning of the last century. The notion of generic complexity was introduced in a 2003 paper, where authors showed that for a large class of finitely generated groups the generic time complexity of some classical decision problems from combinatorial group theory, namely the word problem, conjugacy problem and membership problem, are linear. A detailed introduction of generic case complexity can be found in the surveys.

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Article summary

Generic-case complexity is a subfield of computational complexity theory that studies the complexity of computational problems on "most inputs". Generic-case complexity is a way of measuring the complexity of a computational problem by neglecting a small set of unrepresentative inputs and considering worst-case complexity on the rest. Small is defined in terms of asymptotic density. The apparent efficacy of generic case complexity is because for a wide variety of concrete computational problems, the most difficult instances seem to be rare. Typical instances are relatively easy. This approach to complexity originated in combinatorial group theory, which has a computational tradition going back to the beginning of the last century. The notion of generic complexity was introduced in a 2003 paper, where authors showed that for a large class of finitely generated groups the generic time complexity of some classical decision problems from combinatorial group theory, namely the word problem, conjugacy problem and membership problem, are linear. A detailed introduction of generic case complexity can be found in the surveys.

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Discussion questions

  1. Summarise the article in your own words. Which single claim would you verify first, and why?
  2. Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
  3. If two sources disagreed about one of these facts, what would you need in order to trust one over the other?

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Key claims and bibliography are generated from the same tracked claims and sources as the article page.