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Jul 24, 2020

README.md

JavaSMT

Build Status Build Status on Windows Code Quality Test Coverage Apache 2.0 License Maven Central

JavaSMT is a common API layer for accessing various SMT solvers. The API is optimized for performance (using JavaSMT has very little runtime overhead compared to using the solver API directly), customizability (features and settings exposed by various solvers should be visible through the wrapping layer) and type-safety (it shouldn't be possible to add boolean terms to integer ones at compile time) sometimes at the cost of verbosity.

Quick links

Getting Started | Documentation | Known Issues | Documentation for Developers | Changelog | Configuration Options

References

Feature overview

JavaSMT can express formulas in the following theories:

  • Integer
  • Rational
  • Bitvector
  • Floating point
  • Array
  • Uninterpreted Function

Currently JavaSMT support several SMT solvers (see Getting Started for installation):

The following features are supported (depending on the used SMT solver):

  • Satisfiability checking
  • Quantifiers and quantifier elimination
  • Incremental solving with assumptions
  • Incremental solving with push/pop
  • Multiple independent contexts
  • Model generation
  • Interpolation, including tree and sequential structure
  • Formula transformation using built-in tactics
  • Formula introspection using visitors

Multithreading Support

The solvers Z3(w and w/o Optimization), SMTInterpol, Princess, MathSAT5, Boolector and CVC4 support multithreading, provided that different threads use different contexts, and all operations on a single context are performed from a single thread. Interruption using ShutdownNotifier may be used to interrupt a a solver from any thread. CVC4 supports multithreading on a single context with multiple stacks(=provers).

Garbage Collection in Native Solvers

JavaSMT exposes an API for performing garbage collection on solvers implemented in a native language. As a native solver has no way of knowing whether the created formula object is still referenced by the client application, this API is necessary to avoid leaking memory. Note that due to the hash consing usage inside the solvers, there is never more than one copy of an identical formula object in memory. Consequently, if all created formulas are later re-used (or re-created) in the application, it is not necessary to perform any garbage collection at all.

Z3

The parameter solver.z3.usePhantomReferences may be used to control whether JavaSMT will attempt to decrease references on Z3 formula objects once they are no longer referenced.

MathSAT5

Currently we do not support performing garbage collection for MathSAT5.

Getting started

Installation is possible via Maven, Ivy, or manually. Please see our Getting Started Guide.

Usage

// Instantiate JavaSMT with SMTInterpol as backend (for dependencies cf. documentation)
try (SolverContext context = SolverContextFactory.createSolverContext(
        config, logger, shutdownNotifier, Solvers.SMTINTERPOL)) {
  IntegerFormulaManager imgr = context.getFormulaManager().getIntegerFormulaManager();

  // Create formula "a = b" with two integer variables
  IntegerFormula a = imgr.makeVariable("a");
  IntegerFormula b = imgr.makeVariable("b");
  BooleanFormula f = imgr.equal(a, b);

  // Solve formula, get model, and print variable assignment
  try (ProverEnvironment prover = context.newProverEnvironment(ProverOptions.GENERATE_MODELS)) {
    prover.addConstraint(f);
    boolean isUnsat = prover.isUnsat();
    assert !isUnsat;
    try (Model model = prover.getModel()) {
      System.out.printf("SAT with a = %s, b = %s", model.evaluate(a), model.evaluate(b));
    }
  }
}

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