set(predicate_elim). % default set clear(predicate_elim).
If this flag is set, Prover9 applies a procedure that attempts to eliminate predicate symbols from the problem before the start of the search. The eliminations occur by resolution, and those steps show up as ordinary resolution inferences in any proofs that are found. The procedure works by selecting an eliminable predicate symbol, say P, then doing some set of resolution inferences on P, then removing all clauses that contain P. The procedure is intended to preserve unsatisfiability.
assign(fold_denial_max, n). % default n=0, range [-1 .. INT_MAX]
This parameter applies to negated ground input equalities in which neither side is a constant, say f(a,b) != f(b,a). If the left-hand side has fewer than n symbols, a new constant is introduced and set equal to the left-hand side. This operation is applied to at most one clause in the input sos list.
set(sort_initial_sos). clear(sort_initial_sos). % default clear
If this flag is set, the sos list is sorted just before the start of the search. The order (somewhat arbitrary) is
- positive clauses < negative clauses < mixed clauses;
- fewer symbols < more symbols;
- fewer literals < more literals;
- shallower < deeper.
set(hands_off_options). clear(hands_off_options). % default clear
If this flag is clear, a few other options may be automatically changed, based on the structure of the clauses. For example,factoring ,back unit deletion , will be enabled if any non-Horn clauses are present.A message will be sent to the output file if any changes are mode. This flag is independent of any of the "auto" flags.
set(process_initial_sos). % default set clear(process_initial_sos).
If this flag is set, clauses in the initial sos list will be handled (with a few exceptions) as if they were inferred. For example, demodulation, subsumption, and the check for unit conflict will be applied. The exceptions are that max_weight, max_vars, and max_literals will not be applied.This flag should be cleared only in very rare circumstances.