attribute a weight to a clause. The smaller, the better (lightweight clauses will be favored). A weight must always be positive; the weight of the empty clause should alwyays be 0.

Use Literal.heuristic_weight

Returns the penalty of the clause

Favor clauses with only negative ground lits

Favor clauses that have at least one non-(ground negative) lit

The closest a clause is from the initial goal, the lowest its weight. Some threshold is used for clauses that are too far away

Combine a list of pairs w, coeff where w is a weight function, and coeff a strictly positive number. This is a weighted sum of weights.