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Electronic Colloquium on Computational Complexity

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Reports tagged with QBF:
TR08-076 | 17th June 2008
Ryan Williams

Non-Linear Time Lower Bound for (Succinct) Quantified Boolean Formulas

We prove a model-independent non-linear time lower bound for a slight generalization of the quantified Boolean formula problem (QBF). In particular, we give a reduction from arbitrary languages in alternating time t(n) to QBFs describable in O(t(n)) bits by a reasonable (polynomially) succinct encoding. The reduction works for many reasonable ... more >>>

TR12-059 | 14th May 2012
Rahul Santhanam, Ryan Williams

Uniform Circuits, Lower Bounds, and QBF Algorithms

We explore the relationships between circuit complexity, the complexity of generating circuits, and circuit-analysis algorithms. Our results can be roughly divided into three parts:

1. Lower Bounds Against Medium-Uniform Circuits. Informally, a circuit class is ``medium uniform'' if it can be generated by an algorithmic process that is somewhat complex ... more >>>

TR12-096 | 17th July 2012
Albert Atserias, Sergi Oliva

Bounded-width QBF is PSPACE-complete

Revisions: 3

Tree-width is a well-studied parameter of structures that measures their similarity to a tree. Many important NP-complete problems, such as Boolean satisfiability (SAT), are tractable on bounded tree-width instances. In this paper we focus on the canonical PSPACE-complete problem QBF, the fully-quantified version of SAT. It was shown by Pan ... more >>>

TR14-120 | 16th September 2014
Olaf Beyersdorff, Leroy Chew, Mikolas Janota

Proof Complexity of Resolution-based QBF Calculi

Proof systems for quantified Boolean formulas (QBFs) provide a theoretical underpinning for the performance of important
QBF solvers. However, the proof complexity of these proof systems is currently not well understood and in particular
lower bound techniques are missing. In this paper we exhibit a new and elegant proof technique ... more >>>

TR15-133 | 12th August 2015
Olaf Beyersdorff, Ilario Bonacina, Leroy Chew

Lower bounds: from circuits to QBF proof systems

A general and long-standing belief in the proof complexity community asserts that there is a close connection between progress in lower bounds for Boolean circuits and progress in proof size lower bounds for strong propositional proof systems. Although there are famous examples where a transfer from ideas and techniques from ... more >>>

TR15-152 | 16th September 2015
Olaf Beyersdorff, Leroy Chew, Meena Mahajan, Anil Shukla

Are Short Proofs Narrow? QBF Resolution is not Simple.

The groundbreaking paper `Short proofs are narrow - resolution made simple' by Ben-Sasson and Wigderson (J. ACM 2001) introduces what is today arguably the main technique to obtain resolution lower bounds: to show a lower bound for the width of proofs. Another important measure for resolution is space, and in ... more >>>

TR16-005 | 22nd January 2016
Olaf Beyersdorff, Leroy Chew, Mikolas Janota

Extension Variables in QBF Resolution

We investigate two QBF resolution systems that use extension variables: weak extended Q-resolution, where the extension variables are quantified at the innermost level, and extended Q-resolution, where the extension variables can be placed inside the quantifier prefix. These systems have been considered previously by Jussila et al. '07 who ... more >>>

TR16-043 | 23rd February 2016
Mikolas Janota

On Q-Resolution and CDCL QBF Solving

Q-resolution and its variations provide the underlying proof
systems for the DPLL-based QBF solvers. While (long-distance) Q-resolution
models a conflict driven clause learning (CDCL) QBF solver, it is not
known whether the inverse is also true. This paper provides a negative
answer to this question. This contrasts with SAT solving, ... more >>>

TR16-048 | 11th March 2016
Olaf Beyersdorff, Leroy Chew, Renate Schmidt, Martin Suda

Lifting QBF Resolution Calculi to DQBF

We examine the existing Resolution systems for quantified Boolean formulas (QBF) and answer the question which of these calculi can be lifted to the more powerful Dependency QBFs (DQBF). An interesting picture emerges: While for QBF we have the strict chain of proof systems Q-Resolution < IR-calc < IRM-calc, the ... more >>>

TR18-102 | 15th May 2018
Olaf Beyersdorff, Leroy Chew, Judith Clymo, Meena Mahajan

Short Proofs in QBF Expansion

For quantified Boolean formulas (QBF) there are two main different approaches to solving: QCDCL and expansion solving. In this paper we compare the underlying proof systems and show that expansion systems admit strictly shorter proofs than CDCL systems for formulas of bounded quantifier complexity, thus pointing towards potential advantages of ... more >>>

TR18-172 | 11th October 2018
Olaf Beyersdorff, Joshua Blinkhorn, Meena Mahajan

Building Strategies into QBF Proofs

Strategy extraction is of paramount importance for quantified Boolean formulas (QBF), both in solving and proof complexity. It extracts (counter)models for a QBF from a run of the solver resp. the proof of the QBF, thereby allowing to certify the solver's answer resp. establish soundness of the system. So far ... more >>>

TR18-178 | 9th October 2018
Leroy Chew

Hardness and Optimality in QBF Proof Systems Modulo NP

Quantified Boolean Formulas (QBFs) extend propositional formulas with Boolean quantifiers. Working with QBF differs from propositional logic in its quantifier handling, but as propositional satisfiability (SAT) is a subproblem of QBF, all SAT hardness in solving and proof complexity transfers to QBF. This makes it difficult to analyse efforts dealing ... more >>>

TR19-157 | 25th September 2019
Leroy Chew, Judith Clymo

How QBF Expansion Makes Strategy Extraction Hard

In this paper we show that the QBF proof checking format QRAT (Quantified Resolution Asymmetric Tautologies) by Heule, Biere and Seidl cannot have polynomial-time strategy extraction unless P=PSPACE. In our proof, the crucial property that makes strategy extraction PSPACE-hard for this proof format is universal expansion, even expansion on a ... more >>>

TR20-112 | 8th June 2020
Joshua Blinkhorn

Simulating DQBF Preprocessing Techniques with Resolution Asymmetric Tautologies

Dependency quantified Boolean formulas (DQBF) describe an NEXPTIME-complete generalisation of QBF, which in turn generalises SAT. QRAT is a recently proposed proof system for quantified Boolean formulas (QBF), which simulates the full suite of QBF preprocessing techniques and thus forms a uniform proof checking format for solver verification.

In this ... more >>>

TR20-159 | 9th October 2020
Leroy Chew, Marijn Heule

Relating existing powerful proof systems for QBF

We advance the theory of QBF proof systems by showing the first simulation of the universal checking format QRAT by a theory-friendly system. We show that the sequent system G fully p-simulates QRAT, including the Extended Universal Reduction (EUR) rule which was recently used to show QRAT does not ... more >>>

TR20-188 | 12th December 2020
Olaf Beyersdorff, Joshua Blinkhorn, Meena Mahajan, Tomáš Peitl, Gaurav Sood

Hard QBFs for Merge Resolution

We prove the first proof size lower bounds for the proof system Merge Resolution (MRes [Olaf Beyersdorff et al., 2020]), a refutational proof system for prenex quantified Boolean formulas (QBF) with a CNF matrix. Unlike most QBF resolution systems in the literature, proofs in MRes consist of resolution steps together ... more >>>

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