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Electronic Colloquium on Computational Complexity

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All reports by Author Judith Clymo:

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 >>>

TR19-076 | 24th May 2019
Leroy Chew, Judith Clymo

The Equivalences of Refutational QRAT

The solving of Quantified Boolean Formulas (QBF) has been advanced considerably in the last two decades. In response to this, several proof systems have been put forward to universally verify QBF solvers.
QRAT by Heule et al. is one such example of this and builds on technology from DRAT, ... 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 >>>

TR18-025 | 1st February 2018
Olaf Beyersdorff, Judith Clymo

More on Size and Width in QBF Resolution

In their influential paper `Short proofs are narrow -- resolution made simple', Ben-Sasson and Wigderson introduced a crucial tool for proving lower bounds on the lengths of proofs in the resolution calculus. Over a decade later their technique for showing lower bounds on the size of proofs, by examining the ... more >>>

TR18-024 | 1st February 2018
Olaf Beyersdorff, Judith Clymo, Stefan Dantchev, Barnaby Martin

The Riis Complexity Gap for QBF Resolution

We give an analogue of the Riis Complexity Gap Theorem for Quanti fied Boolean Formulas (QBFs). Every fi rst-order sentence $\phi$ without finite models gives rise to a sequence of QBFs whose minimal refutations in tree-like Q-Resolution are either of polynomial size (if $\phi$ has no models) or at least ... more >>>

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