I build the formula in z3 using the java API.
However, I have some formula that are difficult to solve, and I want to investigate why. Therefore, I want to print the formula in SMTLIB2 format.
Is it possible to get that from a Solver object. Currently, what I can get is only an array of assertions. Thank you.
Yes, Solver.toString() does that. This should also include the variable/constant declarations if you are using the latest master; I think that part was added after the last release.
Related
I'm trying to inspect a simple looping program that finds the maximal element in an integer array. Here is the permalink here. Everything works fine, but I'm really interested in
the resulting SMT file, so I extracted it using:
$ dafny /compile:3 /proverLog:./mySMT.smt myCode.dfy
Then ran with z3 as follows:
$ z3 ./mySMT.smt
I got 3 unsat responses and I was wondering what are the corresponding 3 queries?
I looked at the *.smt file and found 11K of machine-generated SMT.
Any tips on deciphering the smt file? thanks!
If you want the resulting SMT file, then that 11K file is your answer. I imagine that looking at it will lead you to the conclusion that you don't actually want to look at the resulting SMT file.
So, I don't know what it is that you want to accomplish. If you want to learn more about your program, then the best way is to work (only) from the Dafny program text. For example, you can add more assert statements to, essentially, ask the verifier if the given condition is provable at the location of the statement.
If you're interested in how Dafny encodes its verification conditions (that is, if you yourself are a tool developer and want to learn how to generate good verification conditions), then I suggest you use the /print switch to generate the Boogie program that Dafny generates. With some understanding of the Boogie intermediate verification language, the Boogie code is readable. For a more tutorial account of how to encode a Dafny-like language into Boogie, I recommend:
"Specification and verification of object-oriented software",
K. Rustan M. Leino.
Lecture note, Marktoberdorf 2008.
Rustan
PS. Unless you insist on particular formatting, you can print your array elements without using a loop if you first convert the array's element to a sequence:
print "a = ", a[..], "\n";
Here x and k are integers
and the formula is: (50<=x+k Ʌ x+k<51)
Can it get simplified to "x+k=50"
I want the right set of tactics to solve this conjunction of inequalities.
Z3 is not a general purpose symbolic engine to simplify such expressions. Even if you got a good combination of tactics to give you what you need today, the results might change in further releases of the tool. You should look at other systems. Even a symbolic-engine like wolfram-alpha may not produce what you exactly want; but it might give you some alternative forms that might be easier to work with. See here: http://www.wolframalpha.com/input/?i=50%3C%3Dx%2Bk+%26%26+x%2Bk%3C51
I thought I read somewhere that Z3 has some option for returning the model with the "least" value eg given something like
x >= 2
Z3 would return 2. I could swear that I saw some reference to this recently, but I am unable to find it now. Can anyone confirm this?
No, Z3 does not produce 'least' models. However, a separate branch of Z3 that adds optimization features is being developed at the moment (the branch is called `opt'), and perhaps will later be integrated into Z3 proper. A tutorial for the current optimization features is available here: Z3Opt Guide
I'm trying to make z3 (I'm using z3py) to simplify some formulas for me (so that I can have more or less human-readable output). Using ctx-solver-simplify tactic seemed a good choice for me since in a couple of passes it would produce nice compact formulas. But soon I've run into a situation when the output of ctx-solver-simplify does not seem to be equivalent to the original formula (it looks more like being satisfiability-equivalent or so). Also, it might be the case that I'm not dealing with tactics correctly.
Here's what I was trying to do: http://rise4fun.com/Z3Py/g5sX. So, I construct a formula Set2 (everything before the definition of Set2 is just a setup needed to define it) which has a particular satisfying assignment. After applying ctx-solver-simplify, I get a single formula (as a goal) for which this assignment is not satisfying. So what am I dong wrong?
Am I wrong assuming that ctx-solver-simplify would produce an equivalent formula?
Am I handling the tactics and their output in the wrong way?
Anything else?
Thanks.
I have been looking into this, but have so far been unable to reproduce the bug directly
with our current branch. A bug in the context simplifier was fixed a little while ago, and it could
be manifesting itself with the online version of Z3.
There are still a few things I can do to double check if we can reproduce the bug
and I will update this post with what I find.
Hi I am new to Z3 SMT solver. I know you can invoke Z3 programmatically by using relevant APIs. But I want to do the following things with Z3 SMT solver:
how can I feed Z3 with one input file programmatically?
how can I incrementally get the solution(s)?
For example:
while ((check-sat) returns sat)
get the assignments for all boolean vairables
Finally, how can I ask Z3 to save the results into one output file after solving the formula?
Any ideas or documents I can look at?
Thanks million!!!
The Z3 distribution contains several (programmatic API) examples.
examples/c/test_capi.c: many small examples using the C interface.
examples/dotnet/test_managed.cs: similar examples in C#
examples/maxsat/maxsat.c: MaxSAT procedures (in C) on top of the Z3 API.
examples/ocaml/test_mlapi.ml: examples in ML
examples/theory/test_user_theory.c: example showing how to implement an external theory (plugin).