Open-WBO MaxSAT Solver

Version 2.1 - September 2018

Open-WBO is an extensible and modular open-source MaxSAT Solver. Open-WBO was one of the best solvers in the partial MaxSAT categories at MaxSAT Evaluations 2014, 2015, 2016 and 2017 and in the decision and optimization for SMALLINT categories at PB Evaluation 2016.

MaxSAT Evaluation 2018

The default algorithms used by Open-WBO in the complete track are:

• unweighted: Part-MSU3
• weighted: OLL

Usage of the solver: ./open-wbo [options]

The following options are available in Open-WBO:

Global Options

Formula type (0=MaxSAT, 1=PB)

-formula = <int32> [ 0 .. 1] (default: 0)

Print model

-print-model, -no-print-model (default on)

Write unsatisfied soft clauses to file

-print-unsat-soft = <output-file>

Verbosity level (0=minimal, 1=more)

-verbosity = <int32> [ 0 .. 1] (default: 1)

Search algorithm (0=wbo,1=linear-su,2=msu3,3=part-msu3,4=oll,5=best)

-algorithm = <int32> [ 0 .. 1] (default: 5)

BMO search

-bmo,-no-bmo (default on)

Pseudo-Boolean encodings (0=SWC,1=GTE, 2=Adder)

-pb = <int32> [ 0 .. 1] (default: 1)

At-most-one encodings (0=ladder)

-amo = <int32> [ 0 .. 0] (default: 0)

Cardinality encodings (0=cardinality networks, 1=totalizer, 2=modulo totalizer)

-cardinality = <int32> [ 0 .. 2] (default: 1)

WBO Options (algorithm=0, unsatisfiability-based algorithm)

Weight strategy (0=none, 1=weight-based, 2=diversity-based)

-weight-strategy = <int32> [ 0 .. 2] (default: 2)

Symmetry breaking

-symmetry, -no-symmetry (default on)

Limit on the number of symmetry breaking clauses

-symmetry-limit = <int32> [ 0 .. imax] (default: 500000)

PartMSU3 OPTIONS (algorithm=3, partition-based algorithm)

Graph type (0=vig, 1=cvig, 2=res)

-graph-type = <int32> [ 0 .. 2] (default: 2)

Partition strategy (0=sequential, 1=sequential-sorted, 2=binary)

-partition-strategy = <int32> [ 0 .. 2] (default: 2)

Output of solver

Open-WBO follows the standard output of MaxSAT solvers:

• Comments ("c " lines)
• Solution Status ("s " line):
  • s OPTIMUM FOUND : an optimum solution was found
  • s UNSATISFIABLE : the hard clauses are unsatisfiable
  • s SATISFIABLE : a solution was found but optimality was not proven
• Solution Cost Line ("o " lines):
  • This represents the cost of the best solution found by the solver. The cost of a solution is given by the sum of the weights of the unsatisfied soft clause.
• Solution Values (Truth Assignment) ("v " lines):
  • This represents the truth assignment (true/false) assigned to each variable. A literal is denoted by an integer that identifies the variable and the negation of a literal is denoted by a minus sign immediately followed by the integer of the variable.

Authors: Ruben Martins, Vasco Manquinho, Ines Lynce

Contributors: Miguel Neves, Norbert Manthey, Saurabh Joshi, Mikolas Janota

To contact the authors please send an email to: open-wbo@sat.inesc-id.pt