# Tag Info

Accepted

### Counting the number of satisfying assignments in a POSITIVE CNF-SAT

This is still #P-complete . This problem is usually referred to as montone (#)SAT. Monotone #2-SAT is already #P-complete (this is equivalent to counting vertex covers of a graph).  Roth, Dan. "...
Accepted

### The complexity of counting simple paths in a directed graph

The #P-completeness proof of counting simple s-t paths in both undirected and directed graphs can be found in: Leslie G. Valiant: The Complexity of Enumeration and Reliability Problems. SIAM J. ...

### Status of PP-completeness of MAJ3SAT

Hopefully the following paper finally resolves this question: it says that MAJORITY 3SAT is in polynomial time. (And it proves a bunch of other unexpected results on related problems.) https://arxiv....

### Easy problems with hard counting versions

One interesting example from number theory is expressing a positive integer as a sum of four squares. This can be done relatively easily in random polynomial time (see my 1986 article with Rabin at ...

### Easy problems with hard counting versions

A very nice and simple example from Graph Theory is counting the number of Eularian circuits in an undirected graph. The decision version is easy (... and the Seven Bridges of Königsberg problem has ...
Accepted

### Probability of generating a desired permutation by random swaps

I think that whether p>0 can be decided in polynomial time. The problem in question can be easily cast as the edge-disjoint paths problem, where the underlying graph is a planar graph consisting ...

### Counting the number of satisfying assignments in a POSITIVE CNF-SAT

This problem is Monotone-SAT. It is #P-Complete under Cook Reductions. It is one of those problems that are "easy to decide but hard to count." I recommend the following paper. Self-Reducibility of ...
Accepted

### Above #P and counting search problems

If the function f is in #P, then given an input string x of some length N, the value f(x) is a nonnegative number bounded by $2^{poly(N)}$. (This follows from the definition, in terms of number of ...

Accepted

### What's the complexity of counting odd nodes in graph?

Well, at least $\#\mathsf{P}$-hard. Given a SAT formula, construct a graph with two vertices, $v_x$ and $v_x'$, for every possible assignment of variables $\vec{x}$. If $x$ is a satisfying assignment ...
Accepted

### $⊕P$-completeness of $⊕2SAT$

It is shown to be $\oplus P$-complete by Faben: https://arxiv.org/abs/0809.1836 See Thm 3.5. Note that counting independent sets is same as counting solutions to monotone 2CNF.

### Does $\# \mathsf{P}\subseteq \mathsf{FP}^{\mathsf{PH}}$?

If your statement holds, then the polynomial hierarchy collapses: $\mathsf{\# P} \subseteq \mathsf{FP}^{\mathsf{PH}}$ iff $\mathsf{\# P} \subseteq \mathsf{FP}^{\mathsf{\Sigma_k P}}$ for some fixed $k$ ...
Accepted

### Almost uniform sampling implies approximate counting

Given a set $A \subseteq B$, if you can sample uniformly from $B$, then you can estimate by repeated sampling the probability of the event that the sample is in $A$. That is, you can approximate the ...
Accepted

### Easy problems with hard counting versions

Here's a truly excellent example (I may be biased). Given a partially ordered set: a) does it have a linear extension (i.e., a total order compatible with the partial order)? Trivial: All posets ...
Accepted

### Was counting complexity first introduced by Valiant in 1979?

Yes, the complexity class $\mathsf{\#P}$ is first introduced in Valiant's seminal paper "The complexity of computing the permanent." TCS, (1979). This is very clear. As for the terminology, strictly ...
Accepted

### Concrete examples of $\sharp P_1$ complete problems? Self avoiding walks?

As someone with a long time interest in this complexity class, I don't believe there has been any significant work on $\#P_1$ since. (I was a Ph.D. student of Mitsu Ogihara, the second author of the ...
Accepted

### Is this a known problem, and is it #P-complete?

To Question 1: The graphs induced by such edge sets are known as pseudoforests. As your proof of the membership to #P implies, an edge set is the image of a selection function if and only if the graph ...
Accepted

### #P- vs PP-Completeness

Not necessary. Imagine the following Fake-#SAT problem: possible solutions are extended by one bit, and all vectors with this bit set are solutions. That is, the number of satisfying assignments for ...
Accepted

### Is it known whether counting $q$-dimensional $p$-matching is $\#W$-Hard?

Our recent paper shows that counting k-matchings is #W-hard even in bipartite graphs. This answers your question. Radu Curticapean, Dániel Marx: Complexity of counting subgraphs: only the ...

### Is #CYCLE #P-complete?

This is one of the problems (very briefly) discussed by Valiant, "The Complexity of Enumeration and Reliability Problems", SIAM J. Comput. 1979, doi:10.1137/0208032. See the mention of "elementary ...