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.Comment: preprint of a paper to be published at SAT 2019, LNCS, Springer,
including appendi
