QRATPre+: Effective QBF Preprocessing via Strong Redundancy Properties

Abstract

We present version 2.0 of QRATPre+, a preprocessor for quantified Boolean formulas (QBFs) based on the QRAT proof system and its generalization QRAT + . These systems rely on strong redundancy properties of clauses and universal literals. QRATPre+ is the first implementation of these redundancy properties in QRAT and QRAT + used to simplify QBFs in preprocessing. It is written in C and features an API for easy integration in other QBF tools. We present implementation details and report on experimental results demonstrating that QRATPre+ improves upon the power of state-of-the-art preprocessors and solvers.

QBFRelay, QRATPre+, and DepQBF: Incremental Preprocessing Meets Search-Based QBF Solving

“…These results emphasize the benefits of incremental preprocessing compared to single preprocessors, given that we allowed 1800s for preprocessing and solving for the results reported in the tables above. We refer to related work [25] for an additional evaluation of preprocessing using combinations of Bloqqer, HQSpre, and QRATPre + . On 2QBF instances, we omitted DepQBF-prefix-opt in the evaluation because prefix optimization does not have any effects there.…”

“…Generalizing the QRAT Proof System for Preprocessing. QRATPre + [25] is a QBF preprocessor that implements redundancy removal based on a generalization of the QRAT proof system [11], called QRAT + [24]. The QRAT proof system simulates virtually all techniques applied in QBF reasoning tools, including expansion and long-distance resolution [14], and allows for a complete workflow of preprocessing, solving, and certifying QBFs [7].…”

“…The QRAT proof system simulates virtually all techniques applied in QBF reasoning tools, including expansion and long-distance resolution [14], and allows for a complete workflow of preprocessing, solving, and certifying QBFs [7]. In the following, we present the high-level idea of preprocessing based on QRAT and QRAT + and refer to a related tool paper [25] for implementation details of QRATPre + .…”

“…QBFEVAL'18 1. is the 2018 edition in a series of competitive QBF evaluations with the goal to drive the development of QBF reasoning tools. We describe the tool packages we submitted to QBFEVAL'18, which include our search-based QBF solver DepQBF [21,23], the preprocessing module QBFRelay, and the preprocessor QRATPre + [24,25]. QBFRelay is a front end used to apply effective preprocessing by running several preprocessors iteratively and incrementally on the given QBF.…”

Approximate Counting of Minimal Unsatisfiable Subsets

“…We employed several external tools to implement . In particular, we use the QBF solver CAQE [ 49 ] for solving the QBF formula MUSInCell, the 2QBF solver CADET [ 50 ] for solving our -QBF encoding while computing , and the QBF preprocessor QRATPre+ [ 37 ] for preprocessing/simplifying our QBF encodings. Moreover, we employ muser2 [ 7 ] for a single MUS extraction while computing , a MaxSAT solver UWrMaxSat [ 48 ] to implement the algorithm by Marques-Silva et al [ 38 ] for computing the lean kernel of F , and finally, we use a toolkit called pysat [ 27 ] for encoding cardinality constraints used in the formula MUSInCell.…”