Beyond Value Iteration for Parity Games: Strategy Iteration with Universal Trees

  title={Beyond Value Iteration for Parity Games: Strategy Iteration with Universal Trees},
  author={Zhuan Khye Koh and Georg Loho},
Parity games have witnessed several new quasi-polynomial algorithms since the breakthrough result of Calude et al. (STOC 2017). The combinatorial object underlying these approaches is a universal tree , as identified by Czerwiński et al. (SODA 2019). By proving a quasi-polynomial lower bound on the size of a universal tree, they have highlighted a barrier that must be overcome by all existing approaches to attain polynomial running time. This is due to the existence of worst case instances… 

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