Davis Putnam (DPLL)

Procedure DPLL (CNF formula: ?)

If ? is empty, return yes.

If there is an empty clause in ? return no.

If there is a pure literal u in ? return DPLL(?(u)).

If there is a unit clause {u} in ? return DPLL(?(u)).

Else

Select a variable v mentioned in ?.

If DPLL(?(v))=yes,

then return yes.

Else

return DPLL(?(?v)).

[1962]

Recall: ?(u) means set u := true in ?, then simplify