Optimistic Approach
Optimization of rollbacks:
(a) Lazy Cancellation
This method deals with messages. Processes do not immediately send that anti-messages for any roll back computation. Instead, they wait to see if the re-execution of the computation regenerates the same messages; if the same message is recreated, there is no need to cancel the message.
Aggressive cancellation will not perform better than the critical path execution time, lazy cancellation can perform arbitrarily better or worse depending on details of the application and the number of available processors. Empirical evidence suggests that lazy cancellation tends to perform as well, or better than, aggressive cancellation in practice.