Commutative

In Arcology's optimistic concurrency control, commutative variables are the ones that can take concurrent delta updates in a parallel computing environment as long as these updates don't make the result values to overflow or underflow. The final value of the variables will be the same regardless of how the delta updates are applied.

U256Cumulative is a concurrent variable that supports concurrent addition and subtraction. It is conceptionally similar to an atomic integer but with one major constraint: the value can be only update but not read concurrently. Attempting to read while being updated by other threads will result in a transaction rollback.