We know that an NP complete problem with a parsimonious reduction but a many one reduction is candidate problem for NP complete problem not being #P hard.

  1. Likewise is there a possible classification of which P-complete or NL-complete or in general P problems are likely to have counting problems #P-hard and not in #P-hard?

1 Answer 1


Look here: "The Complexity of Counting Functions with Easy Decision Version"

by Zachos and Pagourtzis.

We investigate the complexity of counting problems that belong to the complexity class #P and have an easy decision version. These problems constitute the class #PE which has some well-known representatives such as #Perfect Matchings, #DNF-Sat, and NonNegative Permanent. An important property of these problems is that they are all #P-complete, in the Cook sense, while they cannot be #P-complete in the Karp sense unless P = NP.


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