z3 usage problem in java and strange error - z3

Question

I am using Z3 for the constraints check, and I am currently use the java Z3 package.
What I am doing is that and this is my java code:
Context context = new Context();
Solver s=context.mkSolver();
IntExpr i=context.mkIntConst("i");
IntExpr zero=context.mkInt(1);//int i;
BoolExpr initial=context.mkEq(i,zero);//i=0;
IntExpr one=context.mkInt(1); //initial 1
ArithExpr ipp=context.mkAdd(i,one);//i+1
BoolExpr ippResult=context.mkEq(i,ipp);//i=i+1
BoolExpr gtI=context.mkGe(i,zero);
s.add(initial);
s.add(ippResult);
s.add(gtI);
System.out.println(s+"\n\n");
System.out.println(s.check());
And here is the output I have
(declare-fun i () Int)
(assert (= i 1))
(assert (= i (+ i 1)))
(assert (>= i 1))
UNSATISFIABLE
So I don't know why z3 returns that it is not satisfiable? Since i+1>=1 actually, it is so strange. I don't know what code I am writing wrongly. Thanks!

Answer 1

Your program isn't complete; you use gtI but you never defined it. Probably cut-and-paste error.
In any case, your problem is nicely captured by the SMTLib portion of your output:
(declare-fun i () Int)
(assert (= i 1))
(assert (= i (+ i 1)))
(assert (>= i 1))
The second line says i is 1. Third line says i is equal to i+1. Combining these two, the solver deduces that it must be the case that 1 = 2. Which is clearly not true, and hence you get the UNSATISFIABLE result.
I suspect you wanted to create a new variable and use that in creating i+1, perhaps j? But hard to opine without knowing what it is that you are trying to achieve.