python - Solving formulas in parallel with z3 -

let's have z3 solver number of asserted constraints satisfiable. let s set of constraints, verify every constraint in s whether formula still satisfiable when adding constraint solver. can done sequentially in such fashion:

results = []  constraint in s:   solver.push()   solver.add(constraint)   results.append(solver.check() == z3.sat)   solver.pop()  print all(results) 

now, parallelize speed things up, i'm not sure how z3.

here attempt. consider following simple example. variables non negative integers , have sum 1. verify whether every variable x can independently made > 0. case; let x = 1 , assign 0 other variables. here possible parallel implementation:

from multiprocessing import pool functools import partial import z3  def parallel_function(f):     def easy_parallize(f, sequence):         pool   = pool(processes=4)         result = pool.map(f, sequence)          pool.close()         pool.join()          return result      return partial(easy_parallize, f)  def check(v):     global solver     global variables      solver.push()     solver.add(variables[v] > 0)     result = solver.check() == z3.sat     solver.pop()      return result  range = range(1000) solver = z3.solver() variables = [z3.int('x_{}'.format(i)) in range]  solver.add([var >= 0 var in variables]) solver.add(z3.sum(variables) == 1)  check.parallel = parallel_function(check) results = check.parallel(range) print all(results) 

surprisingly works on machine: results sound , faster. however, doubt safe since i'm working on single global solver , can imagine push/pops happen concurrently. there clean/safe way achieve z3py?

indeed, might work first test, not in general. parallel solving on single context not supported , there data races , segfaults later.

in python, context object hidden, users won't have deal it, run things in parallel, need set 1 context per thread , pass right 1 other functions (which implicitly used hidden context before). note expressions, solvers, tactics, etc, depend on 1 particular context, if objects need cross boundary need translate them (see translate(...) in astref , similar).

see multi-threaded z3? , when z3 parallel version reactivated?