# Tagged Questions

Questions regarding solver programs for the boolean satisfiability problem.

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### How to choose between UC and PL when using the DPLL algorithm?

We know DPLL algorithm is backtracking + unit propagation + pure literal rule. I have an example. There is one example to solve following Satisfiability problem with DPLL. if assign of "0" to ...
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### How to use an old SAT solver to discover a new one, as is done in The Golden Ticket?

In Lance Fortnow's book The Golden Ticket, he mentions that once you have a polynomial-time algorithm for an NP-complete problem, you can use it to find a faster algorithm. Can you tell me how that is ...
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### Using SMT Solvers in formula checking

I'm currently working on a static analysis work in which I need to check whether a given formula is met or not. I hope the following example clarifies my requirement. Suppose we have a list of three-...
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### How to Modify SAT Solvers to Produce Resolution Refutations for Unsatisfiable Instances?

In recent SAT competitions, there is a Certified UNSAT track. The problem instances are all unsatisfiable and the solvers are asked to produce certificates for unsatisfiability. One way is to produce ...
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### Does MiniSAT need exponential time?

I'm asking for a sequence of instances for SAT, one instance for each length, such that the sequence takes exponential time with MiniSAT.
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### Why is pure literal elimination absent in DPLL-based algorithms like Chaff?

I'm looking into various SAT-solvers and trying to understand how they work and why they are designed in certain ways. (But I'm not in a university at the moment and I do not know anyone who is a ...
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### Assignment to make formula unsatisfiable

Lets imagine we have a satisfiable formula $F(A_0, A_1,...A_k,S_0,...,S_n)$ The problem to solve is "Is there an assignment for variables $(S_0,...,S_n)$ which will make F unsatisfiable?". One way of ...
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### Conflict Driven Clause Learning backtracking clarification

On the wikipedia page here it describes pretty well the CDCL algorithm (and it seems the pictures were taken from slides created by Sharad Malik at Princeton). However when describing how to backtrack ...
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### A query regarding the Max3SAT Approximation Algorithm's Application

Its known that a polynomial time Approximation Algorithm that satisfies 3MaxSAT in 7/8+e clauses implies P=NP. If given that the given 3MaxSAT is satisfiable, it is still difficult to find a 7/8+e ...
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### Why don't modern SAT solvers use the notion of a “watched clause”, in the same way they use the notion of a “watched literal”?

Modern SAT solvers use the notion of "watched literals": when a value is chosen for a literal $l$, the solver only checks whether that falsifies clauses with $l$ in them if $l$ is one of the watched ...
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### Basic question about backjumping in SAT solvers

I am reading "Formalization and Implementation of Modern SAT Solvers", by Filip MariÄ‡. My question is about how backjumping is defined. In an example [1], there is a conflict clause C equal to [-1,-...
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### Are there any open source SAT solvers with UNSAT core extraction algorithm built in?

Just like the title says. I need to use a SAT solver on a series of CNF formulas but not only do I need an answer of the type satisfiable/unsatisfiable but also some subset of clauses whose ...
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### How is the complexity of algorithms to solve 3CNF (decision problem) specified? [duplicate]

For k inputs, the complexity of naive algorithm is O(2^k). I understood this one. What is meant by "the size of the instance to be solved should be polynomial in k". Is it equivalent to the statement ...
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### SAT for arithmetic

Given two integers $X$ and $Y$, each can be encoded in binary $X=(x_4 x_3 x_2 x_1)$ and $Y=(y_4 y_3 y_2 y_1)$, how do I encode the constraint $$|X-Y|\geq n \quad\text{and}\quad|X-Y|= n$$ when $n$ is ...
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### Common method for solving satisfiability problems which lie in P

I know from Schaefer's Dichotomy Theorem that only a few types of satisfiability problems are in P and any other problem is NP-complete. However, all of the algorithms I know for them use specific ...
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### Constrain certain variables in CNF to unique satisfying assignments

[Reposted because the original question was deleted by the poster.] I'm looking for a way to add additional clauses (and maybe additional variables) to an already existing SAT instance so that ...
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So this sounds like this might lead to an undecidable theory but I thought I would give it a try and ask about it after I found nothing on the subject. I am somewhat interested in finding functions ...
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### Why is DPLL better than brute force?

I understand that by being clever about the way we navigate the search space of the SAT problem we're going to get better performance than by randomly choosing and testing solutions, though of course ...
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### Sound and complete algorithms for boolean satifiability

To my best knowledge, these are the sound and complete algorithms for boolean satisfiability Variations of DPLL algorithm (e.g. CDCL, Look-ahead solvers) Stalmarks method Binary Decision Diagram (...
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### Recipe book for SAT encodings?

SAT solvers are getting more and more efficient in solving large instances and are being used as back-ends in various contexts. Every time one wants to use them to solve a problem in a specific domain,...
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### Detection of redundant boolean constraints

I'm trying to solve a constraint programming problem using a SAT solver. I have set of constraints in the form of propositional logic statements, which are converted to CNF using Tseitin ...
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### Introduction to bounded model checking that describes model generation

Most of the tutorials I have found on model checking and bounded model checking start with, the model is given as a Kripke Structure M = (S,I,T,L) where S is a set of states, I is a set of initial ...
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### Solving SAT using tableau calculus

I've learned about tableau calculus which is a decision procedure solving the problem of satisfiability of a first order logic formula. Now I'm wondering why this technique can't be used to solve the ...
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### Fast Consequence FInders

I have been struggling in the search for a modern fast "consequence finder". That is, an implementation based on state-of-the-art theory; things of the ilk of Z3, Prover9, OTTER, etc. To describe ...
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### Multicore SAT Solver

I am trying to solve a 25k clauses 5k variables SAT problem. As it has been running for an hour (precosat) and I'd like to solve bigger ones afterwards, I'm looking for a multi-core SAT-Solver. As ...
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### Convert $\sum x_i = y$ to 3-sat

I have a simple looking question. What is the most efficient conversion of $\sum_{i=1}^n x_i = y$ to 3-sat? Here $x_i$ is either $1$ or $0$ and $y$ is some positive integer. Can you do better than ...
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### Why Is Alloy not an Answer Set Programming system?

Alloy's front page doesn't mention ASP, but the description sounds like ASP (finding solutions consistent with a logical spec). And Alloy isn't listed in the Wikipedia ASP article. Yet ASP systems ...
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### Encoding 1-out-of-n constraint for SAT solvers

I'm using a SAT solver to encode a problem, and as part of the SAT instance, I have boolean variables $x_1,x_2,\dots,x_n$ where it is intended that exactly one of these should be true and the rest ...
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### When to use SAT vs Constraint Satisfaction?

If I have a hard problem, one standard approach is to express it as a SAT instance and try running a SAT solver on it. Another standard approach is to express it as a constraint satisfaction problem, ...
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### Understanding DPLL algorithm

I'm trying to understand DPLL algorithm for solving SAT problem. And here it is: ...
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### Unification vs. SAT solver

I read on Wikipedia that unification is a process of solving the satisfability problem. At the same time, I know that such solvers are called "SAT solvers" or "SMT solvers". So, are they different ...
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### Introduction into first order logic verification

I am trying to teach myself different approaches to software verification. I have read some articles. As far as I learned, propositional logic with temporal generally uses model checking with SAT ...
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### Running time of CDCL compared to DPLL

What's the complexity of Conflict-Driven Clause Learning SAT solvers, compared to DPLL solvers? Was it proven that CDCL is faster in general? Are there instances of SAT that are hard for CDCL but easy ...
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### Can top SAT-solvers factor easy numbers?

Modern SAT-solvers are very good at solving many real-world examples of SAT instances. However, we know how to generate hard ones: for instance use a reduction from factoring to SAT and give the RSA ...
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### Resolution complexity versus a constrained SAT algorithm

EDIT: ad hoc speed-ups are excluded. We have the result that propositional resolution requires exponential time. The resolution result uses the proof of the pigeonhole principle as an example of a ...