Expected Cost | +- [f] | 0 | +- [Program] | 0:While(y ≥ 1 + x) | Tick(1) | x :~ {1 : 1 + x} | 1:While(x ≥ 1 + y) | Tick(1) | y :~ {1 : 1 + y} | +- Expected Cost | | | +- [f] | | 0 | | | +- [Program] | | 0:While(y ≥ 1 + x) | | Tick(1) | | x :~ {1 : 1 + x} | | | +- While.step | | | | | +- [Problem] | | | 0:While(y ≥ 1 + x) | | | Tick(1) | | | x :~ {1 : 1 + x} | | | | | +- [f] | | | 0 | | | | | +- Expected Cost Body | | | | | | | `- [1 | ⊤] | | | | | +- linear-template | | | | | | | `- 1 + [-x + y | -x + y ≥ 0] | | | | | +- [Norms] | | | [[1 | ⊤],[-x + y | -x + y ≥ 0]] | | | | | +- [Invariant] | | | y ≥ 1 + x ==> [1 | ⊤] + h([1 | ⊤],[-1 + -x + y | -1 + -x + y ≥ 0]) ≼ h([1 | ⊤],[-x + y | -x + y ≥ 0]) | | | 1 + x ≥ 1 + y ==> 0 ≼ h([1 | ⊤],[-x + y | -x + y ≥ 0]) | | | | | `- [-x + y | -x + y ≥ 0] | | | `- [-x + y | -x + y ≥ 0] | +- Expected Cost | | | +- [f] | | 0 | | | +- [Program] | | 1:While(x ≥ 1 + y) | | Tick(1) | | y :~ {1 : 1 + y} | | | +- While.step | | | | | +- [Problem] | | | 1:While(x ≥ 1 + y) | | | Tick(1) | | | y :~ {1 : 1 + y} | | | | | +- [f] | | | 0 | | | | | +- Expected Cost Body | | | | | | | `- [1 | ⊤] | | | | | +- linear-template | | | | | | | `- 1 + [x + -y | x + -y ≥ 0] | | | | | +- [Norms] | | | [[1 | ⊤],[x + -y | x + -y ≥ 0]] | | | | | +- [Invariant] | | | x ≥ 1 + y ==> [1 | ⊤] + h([1 | ⊤],[-1 + x + -y | -1 + x + -y ≥ 0]) ≼ h([1 | ⊤],[x + -y | x + -y ≥ 0]) | | | 1 + y ≥ 1 + x ==> 0 ≼ h([1 | ⊤],[x + -y | x + -y ≥ 0]) | | | | | `- [x + -y | x + -y ≥ 0] | | | `- [x + -y | x + -y ≥ 0] | +- Expected Cost | | | +- [f] | | [x + -y | x + -y ≥ 0] | | | +- [Program] | | 0:While(y ≥ 1 + x) | | Tick(1) | | x :~ {1 : 1 + x} | | | +- While.step | | | | | +- [Problem] | | | 0:While(y ≥ 1 + x) | | | Tick(1) | | | x :~ {1 : 1 + x} | | | | | +- [f] | | | [x + -y | x + -y ≥ 0] | | | | | +- linear-template | | | | | | | `- 1 + 2·([-x + y | -x + y ≥ 0]) + [x + -y | x + -y ≥ 0] | | | | | +- [Norms] | | | [[1 | ⊤],[-x + y | -x + y ≥ 0],[x + -y | x + -y ≥ 0]] | | | | | +- [Invariant] | | | y ≥ 1 + x ==> 0 + h([1 | ⊤],[-1 + -x + y | -1 + -x + y ≥ 0],[1 + x + -y | 1 + x + -y ≥ 0]) ≼ h([1 | ⊤],[-x + y | -x + y ≥ 0],[x + -y | x + -y ≥ 0]) | | | 1 + x ≥ 1 + y ==> [x + -y | x + -y ≥ 0] ≼ h([1 | ⊤],[-x + y | -x + y ≥ 0],[x + -y | x + -y ≥ 0]) | | | | | `- [x + -y | x + -y ≥ 0] | | | `- [x + -y | x + -y ≥ 0] | `- [-x + y | -x + y ≥ 0] + [x + -y | x + -y ≥ 0]