Actions

Prover9's actions allow the user to change the search strategy during the search. For example, after a certain number of given clauses have been used, the max_weight can be changed.

Actions can be triggered in two ways:

by some counter, for example, after 100 clauses have been retained, and
when a clause containing an action attribute is used, for example, when it is used in a proof.

Accepted Actions

The currently accepted actions are exit (which terminates the search) and a subset of the ordinary flags and parameters.

Changable flags: reuse_denials, print_gen, print_kept, print_given, breadth_first. lightest_first. breadth_first_hints.
Changable parameters: demod_step_limit, demod_increase_limit, new_constants, para_lit_limit, stats, max_given, max_weight, max_depth, max_vars, max_proofs, max_literals, constant_weight, variable_weight, not_weight, or_weight, prop_atom_weight, nest_penalty, depth_penalty, default_weight, pick_given_ratio, age_part, weight_part, hints_part, false_part, true_part.

Actions Triggered by Counters

Counter actions are given as a list of rules trigger -> action in the input file. Here are the currently recognized triggers for counter actions.

given: the number of given clauses that have been processed.
generated: the number of clauses that have been inferred.
kept: the number of clauses that have been inferred and retained.
level: the search level (this applies to breadth-first searches).

The list must start with list(actions). and end with end_of_list.

Here is an example list of counter actions.

list(actions).

  given=10        -> set(print_kept).
  kept=1000       -> assign(max_weight, 30).
  generated=5000  -> assign(pick_given_ratio, 4).
  level=3         -> exit.

end_of_list.

Actions Triggered by Clauses

Clause actions occur as attributes on clauses, for example,

A * B != B * A  # action(in_proof -> assign(max_weight, 30)).

In this example (which only makes sense if max_proofs > 1), if the clause occurs in a proof, the action is applied.

The only trigger currently recognized for clause actions is in_proof. Others will likely be added.

Next Section: Goals and Denials