Abstract
We introduce a class of counting problems that arise naturally in equational matching and study their computational complexity. If E is an equational theory, then #E-Matching is the problem of counting the number of complete minimal E-matchers of two given terms. #E-Matching is a well-defined algorithmic problem for every finitary equational theory. Moreover, it captures more accurately the computational difficulties associated with finding complete sets of minimal E-matchers than the corresponding decision problem for E-matching does.
In 1979, L. Valiant developed a computational model for measuring the complexity of counting problems and demonstrated the existence of #P- complete problems, i.e., counting problems that are complete for counting non-deterministic Turing machines of polynomial-time complexity. Using the theory of #P-completeness, we analyze the computational complexity of #E-matching for several important equational theories E. We establish that if E is one of the equational theories A, C, AC, I, U, ACI, Set, ACU, or ACIU, then #E-Matching is a #P-complete problem. We also show that there are equational theories, such as the restriction of AC-matching to linear terms, for which the underlying decision matching problem is solvable in polynomial time, while the associated counting matching problem is #P-complete.
Partially supported by Institut National Polytechnique de Lorraine grant 910 0146 R1.
Part of the research reported here was carried out while this author was visiting CRIN & INRIA-Lorraine supported by the University of Nancy 1 and INRIA-Lorraine. Research of this author is also supported by a 1993 John Simon Guggenheim Fellowship and by NSF Grant CCR-9108631.
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© 1994 Springer-Verlag Berlin Heidelberg
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Hermann, M., Kolaitis, P.G. (1994). The complexity of counting problems in equational matching. In: Bundy, A. (eds) Automated Deduction — CADE-12. CADE 1994. Lecture Notes in Computer Science, vol 814. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-58156-1_41
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DOI: https://doi.org/10.1007/3-540-58156-1_41
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