pwbo is a parallel Boolean optimization solver. For the MaxSAT'12 evaluation pwbo is run with two threads.
An unsatisfiability-based algorithm is used to search on the lower bound of the optimal solution, while at the
same time a linear search is performed on the upper bound of the optimal solution.

pwbo2.1 uses a new unsatisfiability-based algorithm that is expected to perform better for partial Weighted MaxSAT.
The upper bound search uses a pseudo-Boolean representation of the objective function.

References:
R. Martins, V. Manquinho, I. Lynce, Clause Sharing in Parallel MaxSAT, LION 2012.
R. Martins, V. Manquinho, I. Lynce, Exploiting Cardinality Encodings in Parallel Maximum Satisfiability, ICTAI 2011.
R. Martins, V. Manquinho, I. Lynce, Parallel Search for Boolean Optimization, RCRA 2011.