Can Z3 output “anything” for unconstrained values of UF?

问题

Some values of uninterpreted functions can be unconstrained during the search. For example, if in smt query only f(1) is called, then f(2), f(3) can be anything. Is there a way (some option may be) to know which values were not used during the solving and therefore can be anything?

回答1:

For quantifier free problems, you can achieve that by using the option :model-partial to true. Here is an example (also available here):

(set-option :model-partial true)

(declare-fun f (Int) Int)

(assert (> (f 0) 0))
(assert (< (f 1) 0))

(check-sat)
(get-model)

In this example, we get the output:

sat
(model 
  (define-fun f ((x!1 Int)) Int
    (ite (= x!1 0) 1
    (ite (= x!1 1) (- 1)
      #unspecified)))
)

BTW, in the next release (Z3 4.3.2), this option is renamed to :model.partial. In the next release, the options are grouped in modules.

来源：https://stackoverflow.com/questions/15388999/can-z3-output-anything-for-unconstrained-values-of-uf