Some silly Z3 scripts I wrote(hillelwayne.com)

46 pointsby azhenleyvor 5 Monaten9 comments

https://www.hillelwayne.com/post/z3-examples/

9 comments

I'm suspicious of the theorem proving example. I thought Z3 could fail to return sat or unsat, but he is assuming that if it's not sat the theorem must be proven

hwaynevor 5 Monaten

...Whoops. Yup, SMT solvers can famously return `unknown` on top of `sat` and `unsat`. Just added a post addendum about the mistake.

ymherklotzvor 5 Monaten

No I think it's fine. On another note, I have proven Fermat's Last Theorem with z3 using this setup :) and it goes faster if you reduce a variable called "timeout" for some reason!

  from z3 import *
  
  s = Solver()
  s.set("timeout", 600)
  a = Int('a')
  b = Int('b')
  c = Int('c')
  s.add(a > 0)
  s.add(b > 0)
  s.add(c > 0)
  theorem = a ** 3 + b ** 3 != c ** 3
  if s.check(Not(theorem)) == sat:
      print(f"Counterexample: {s.model()}")
  else:
      print("Theorem true")

potato-peelervor 5 Monaten

For the curious, solvers like z3 are used in programming languages to verify logic and constraints. Basically it can help find logic issues and bugs during compile time itself, instead of waiting for it to show up in runtime.

https://en.wikipedia.org/wiki/Satisfiability_modulo_theories...

bjornsingvor 5 Monaten

The concept is called static analysis.

ukuinavor 5 Monaten

Seems adjacent, with some overlap.

lkutyvor 5 Monaten

Like in the Dafny pogramming language. Cfr. https://www.youtube.com/watch?v=oLS_y842fMc

mathisfun123vor 5 Monaten

in theory that's what a compiler is - a thin wrapper over a SAT solver. in practice most compilers just use heuristics <shrug>.

iberatorvor 5 Monaten

I was expecting a Z3 computer from Germany.