使用 z3py 的全局参数

Question

I'm trying to use SMT solver over a scheduling problem and could not find anything helping in the documentation.

It seems using following ways of setting parameters do not have any effect on the solver.

from z3 import *

set_param(logic="QF_UFIDL")
s = Optimize() # or even Solver()

or even

from z3 import *

s = Optimize()
s.set("parallel.enable", True)

So how can I set [global] parameters effectively in z3py. to be most specific I need to set parameters below:

1. parallel.enable=True
2. auto_confic=False
3. smtlib2_compliant=True
4. logic="QF_UFIDL"

Answer 1

Use global parameter statements like the following on separate lines before creating Solver or Optimize object:

set_param('parallel.enable', True)
set_param('parallel.threads.max', 4)   #  default 10000

To set non-global parameters specific to a Solver or Optimize object, you can use the help() function to show available parameters:

o = Optimize()
o.help()

s = Solver()
s.help()

The following example shows how to set an Optimize parameter:

opt = Optimize()
opt.set(priority='pareto')

Answer 2

Use set_param , as described here: https://z3prover.github.io/api/html/namespacez3py.html#a4ae524d5f91ad1b380d8821de01cd7c3

It isn't clear what's not working for you. Are you getting an error message back? From your description, I understand that the setting does indeed take place, but you don't see any change in behavior? For that, you'll have to provide a concrete example we can look at. Note that for most parameters, the effects will only be visible with benchmarks that trigger the option, and even then it'll be hard to tell what (if any) effect it had, unless you dig into verbose log output.

Also, parallel-solving features, which you seem to be interested in, isn't going to gain you much. See Section 9.2 of https://z3prover.github.io/papers/z3internals.html : Essentially it boils down to attempting to solve the same problem with different seeds to see if one of them goes faster. If you have many cores lying around it might be worth a try, but don't expect magic out of it.