On symmetric signatures in holographic algorithms

  • Authors:
  • Jin-Yi Cai;Pinyan Lu

  • Affiliations:
  • Computer Sciences Department, University of Wisconsin, Madison, WI;Department of Computer Science and Technology, Tsinghua University, Beijing, P.R. China

  • Venue:
  • STACS'07 Proceedings of the 24th annual conference on Theoretical aspects of computer science
  • Year:
  • 2007

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Abstract

In holographic algorithms, symmetric signatures have been particularly useful.We give a complete characterization of these symmetric signatures over all bases of size 1. These improve previous results [4] where only symmetric signatures over the Hadamard basis (special basis of size 1) were obtained. In particular, we give a complete list of Boolean symmetric signatures over bases of size 1. It is an open problem whether signatures over bases of higher dimensions are strictly more powerful. The recent result by Valiant [18] seems to suggest that bases of size 2 might be indeed more powerful than bases of size 1. This result is with regard to a restrictive counting version of #SAT called #Pl-Rtw-Mon-3CNF. It is known that the problem is #P-hard, and its mod 2 version is ⊕P-hard. Yet its mod 7 version is solvable in polynomial time by holographic algorithms. This was accomplished by a suitable symmetric signature over a basis of size 2 [18]. We show that the same unexpected holographic algorithm can be realized over a basis of size 1. Furthermore we prove that 7 is the only modulus for which such an "accidental algorithm" exists.