A synchronizer is a distributed-computing technique that lets an asynchronous network simulate synchronous rounds. It gives processes a way to know when it is safe to move to the next logical round.
Alpha Synchronizer
In an synchronizer, each process waits until it has received the expected messages for the current round from its neighbors.
The basic pattern is:
- sends an acknowledgement message back to each sender after receiving its message.
- waits until messages from all relevant senders are received.
- Once safe, sends a safe message to its neighbors.
- Processes move to the next round after the local safety condition is satisfied.
Intuition
The synchronizer adds a control protocol around the original distributed algorithm. The original messages do the algorithmic work. The acknowledgement and safe messages coordinate timing.
Tradeoff
The benefit is simpler reasoning: an asynchronous system can be analyzed like a synchronous round-based algorithm. The cost is extra messages and waiting.
This connects to Kogge-Stone Algorithm because both concern communication structure across many processes, but synchronizers solve timing uncertainty while Kogge-Stone solves parallel prefix computation.
One-line Interview Answer
A synchronizer lets asynchronous distributed processes simulate synchronous rounds by using acknowledgement and safe messages.