getunsatcore

getunsatcore is a function or API mechanism provided by many modern SAT and SMT solvers to retrieve an unsatisfiable core after a solve attempt. An unsat core is a subset of the input constraints that already suffices to render the problem unsatisfiable. In practice, solvers compute cores by solving with assumptions or by labeling assertions; the core returned by getunsatcore typically consists of the identifiers (labels or assumption literals) corresponding to the implicated constraints.

Usage typically involves enabling core tracking before solving, labeling constraints or using assumptions, invoking the solver, and, if the result is unsat, requesting the core via getunsatcore. The core can be used for debugging, constraint debugging, or for pruning search in optimization problems. It may also serve as a starting point for core minimization to produce a smaller, more informative unsat core.

Notes: the core is not guaranteed to be unique, and not every solver returns a minimal core. The returned core can depend on solver configuration and internal heuristics. Some solvers offer both exact unsat cores and weakened cores or provide options to minimize them further. In practice, getunsatcore complements other debugging and verification techniques, such as proof logging or trace generation.

See also: unsat core, assumption-based solving, named assertions, core minimization, proof logging.