Z3 Python 中无法满足的核心 [英] Unsatisfiable Cores in Z3 Python
问题描述
我正在使用 Z3 的 Python API,试图在我正在编写的研究工具中包含对它的支持.我有一个关于使用 Python 接口提取不可满足的核心的问题.
I am working with the Python API of Z3 in an attempt to include support for it in a research tool that I am writing. I have a question regarding extracting the unsatisfiable core using the Python interface.
我有以下简单查询:
(set-option :produce-unsat-cores true)
(assert (! (not (= (_ bv0 32) (_ bv0 32))) :named __constraint0))
(check-sat)
(get-unsat-core)
(exit)
通过 z3 可执行文件(对于 Z3 4.1)运行此查询,我收到了预期的结果:
Running this query through the z3 executable (for Z3 4.1), I receive the expected result:
unsat
(__constraint0)
对于 Z3 4.3,我得到一个分段错误:
For Z3 4.3, I obtain a segmentation fault:
unsat
Segmentation fault
这不是主要问题,尽管这是一个有趣的观察.然后我将查询(在文件内)修改为
That isn't the main question, although that was an intriguing observation. I then modified the query (inside a file) as
(assert (! (not (= (_ bv0 32) (_ bv0 32))) :named __constraint0))
(exit)
使用文件处理程序,我将此文件的内容(在变量 `queryStr' 中)传递给以下 Python 代码:
Using a file handler, I passed the contents of this file (in a variable `queryStr') to the following Python code:
import z3
...
solver = z3.Solver()
solver.reset()
solver.add(z3.parse_smt2_string(queryStr))
querySatResult = solver.check()
if querySatResult == z3.sat:
...
elif querySatResult == z3.unsat:
print solver.unsat_core()
我收到来自 `unsat_core' 函数的空列表:[].我是否错误地使用了此功能?该函数的文档字符串表明我应该做类似的事情
I receive the empty list from the `unsat_core' function: []. Am I using this function incorrectly? The docstring for the function suggests that I should instead be doing something similar to
solver.add(z3.Implies(p1, z3.Not(0 == 0)))
但是,我想知道是否仍然可以按原样使用查询,因为它符合 SMT-LIB v2.0 标准(我相信),以及我是否遗漏了一些明显的东西.
However, I was wondering if it were still possible to use the query as is, since it conforms to SMT-LIB v2.0 standards (I believe), and whether I was missing something obvious.
推荐答案
您观察到的崩溃已得到修复,该修复将在下一个版本中提供.如果您尝试不稳定"(正在进行中)分支,您应该得到预期的行为.您可以使用
The crash you observed has been fixed, and the fix will be available in the next release. If you try the "unstable" (work-in-progress) branch, you should get the expected behavior. You can retrieve the unstable branch using
git clone https://git01.codeplex.com/z3 -b unstable
API parse_smt2_string
仅提供对解析 SMT 2.0 格式公式的基本支持.它不保留注释 :named
.我们将在未来版本中解决这个和其他限制.同时,我们应该使用答案文字",例如 p1
和以下形式的断言:
The API parse_smt2_string
provides only basic support for parsing formulas in SMT 2.0 format. It does not keep the annotations :named
. We will address this and other limitations in future versions. In the meantime, we should use "answer literals" such as p1
and assertions of the form:
solver.add(z3.Implies(p1, z3.Not(0 == 0)))
在unstable"分支中,我们还支持以下新 API.它模拟"了 SMT 2.0 标准中使用的 :named
断言.
In the "unstable" branch, we also support the following new API. It "simulates" the :named
assertions used in the SMT 2.0 standard.
def assert_and_track(self, a, p):
"""Assert constraint `a` and track it in the unsat core using the Boolean constant `p`.
If `p` is a string, it will be automatically converted into a Boolean constant.
>>> x = Int('x')
>>> p3 = Bool('p3')
>>> s = Solver()
>>> s.set(unsat_core=True)
>>> s.assert_and_track(x > 0, 'p1')
>>> s.assert_and_track(x != 1, 'p2')
>>> s.assert_and_track(x < 0, p3)
>>> print(s.check())
unsat
>>> c = s.unsat_core()
>>> len(c)
2
>>> Bool('p1') in c
True
>>> Bool('p2') in c
False
>>> p3 in c
True
"""
...
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