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I'm trying to solve a problem using the Array type in z3. Because I need to use BitVec type I declared the array as :

numbers = [BitVec(chr(i), 8) for i in range(0, 4)]

And then :

s = Solver()
s.add(numbers[0] == 100)
s.add(numbers[1] == numbers[0] + 2)
s.add(numbers[3] == numbers[1] + numbers[0])
s.add(numbers[2] == numbers[1] - 4)
print(s.check())
print(s.model())

Output :

sat
[ = 98,  = 202,  = 102,  = 100]

However it doesn't print in order the results, Is there a way to print them in order?

Example:

[ = 100, = 102, = 98, = 202 ]

I have another doubt too. Is there a way to set a limit to the frequencies of a number:

numbers = [BitVec(chr(i), 8) for i in range(0, 4)]

s = Solver()
s.add(numbers[0] == 100)
s.add(numbers[0] + numbers[1] + numbers[2] == 200)
s.add(collections.Counter(numbers)[100] == 1) # something like that
print(s.check())
print(s.model())

To set that number 100 must be present only in numbers[0].

JohanC
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meowmeowxw
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  • Possible duplicate of [How to print z3 solver results print(s.model()) in order?](https://stackoverflow.com/questions/52100801/how-to-print-z3-solver-results-prints-model-in-order) – alias Sep 01 '19 at 18:47
  • See https://stackoverflow.com/questions/52100801/how-to-print-z3-solver-results-prints-model-in-order for your first question. It's always best to ask different questions in different threads on stack-overflow. For frequencies: You'll need to count explicitly and assert a Pb constraint on it. – alias Sep 01 '19 at 18:48
  • How can I implement a counter and assert the constraint on it? – meowmeowxw Sep 01 '19 at 19:13
  • What have you tried? Please formulate it as a separate question and show us what you tried and where it went wrong. – alias Sep 01 '19 at 20:42

1 Answers1

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For your first question, I first propose to give some readable names to the variables. chr(i) for i in range(0, 4) are 4 unprintable characters. Better use chr(i+48) for digits 0..9 or chr(i+65) for letters A..Z

The simplest way to print your result in the same order as the array is just: print ([s.model[n].as_long() for n in numbers]).

For your second question, I propose to use Z3's Sum function. For example:

numbers = [BitVec('N'+chr(i+48), 8) for i in range(0, 4)]
s = Solver()
s.add(numbers[0] == 100)
s.add(numbers[0] + numbers[1] + numbers[2] == 200)
s.add(Sum([If(n == 100, 1, 0) for n in numbers]) == 1)
print(s.check())
m = s.model()
print (m)
print ([m[n].as_long() for n in numbers])

Which outputs (in my test case):

sat
[N3 = 116, N1 = 106, N0 = 100, N2 = 250]
[100, 106, 250, 116]
JohanC
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  • Thanks for the reply, I used in the end `numbers = [BitVec('{:2}'.format(i), 8) for i in range(32)]`, end I sorted the value when the model was ready with: ` m = s.model(); model = sorted([(d, m[d]) for d in m], key = lambda x: str(x[0])) ` – meowmeowxw Nov 01 '19 at 20:59