diff --git a/Concurrent Systems/notes/6 - Atomicity.md b/Concurrent Systems/notes/6 - Atomicity.md index 9a7d052..1552a13 100644 --- a/Concurrent Systems/notes/6 - Atomicity.md +++ b/Concurrent Systems/notes/6 - Atomicity.md @@ -52,8 +52,12 @@ We now show that $\to$ is acyclic. - adjacent edges cannot belong to the same order (e.g. not both $\to_X$), otw. the cycle would be shortable, because of transitivity of the total order! - adjacent edges cannot belong to orders on different objects - this would mean that an operation is involved in both $\to_X$ and $\to_Y$ but it is not possible of course - - Hence, at least one $\to_X$ exists and it must be between two $\to_H$ i.e.: $$op1 \to_H op2 \to_X op3 \to_H op4$$ + - Hence, at least one $\to_X$ exists and it must be between two $\to_H$ i.e.: $$op1 \to_H op2 \to_X op3 \to_H op4$$, with op1 = op4 - can this be a cycle? + - $op1 \to_H op2$ means that $res(op1) <_H inv(op2)$ + - $op2 \to_X op3$ entails that $inv(op2) <_H res(op3)$ + - if not, as is a total order, we would have that $res(op3) <_H inv(op2)$, but we then would have a cycle of lenght 2... + - $op2 \to_H op3$ entails that $inv(op2) <_H res(op3)$ > [!PDF|red] class 6, p.6> we would have a cycle of length