Introduction: -
- First effort- message passing among concurrent task by Brinch Hansen (1978) and Hoare (1978)
- Developed a technique for handling the problem of what to do When multiple simultaneous requests were made by other tasks to communicate with a Given Task
- Some form of non determinism which required to Provide fairness in choosing among Those requests.
- Fairness: - the requester are provided at equal chance of communicating with a Given Task
- Guarded commands: - Non deterministic constructs for statement levelcontrol. Dijkstra 1975th
- basis of the construct.
The concept of synchronous message passing: -
- Either synchronous or asynchronous.
- Synchronous: - tasks are Often busy and busy When They Can not Be interrupted by other units
- EC A and B are in execution and if A wishes to send message to B That would disrupt B's processing (current)
- Alternative is to Provide a linguistic mechanism did Allows a task to specify other task When its ready to receive messages
- Task can be designed so it can suspend its execution did at some point it is idle or Either Because Because it needs information from another unit before it can continue
- some cases sit and wait: - EC, A is waiting for a message at the TimeTask B sends That message, the message can be Transmitted.. It is called Rendezvous
- Rendezvous: - Occur Only When Both sender and receiver want it to happen. Can Be Transmitted in Either or Both directions.
- Cooperation and Competition Synchronization can be handled conveniently handled with message passing model.
No comments:
Post a Comment