Logical Instantaneity and Causal Order: Two ``First Class'' Communication Modes for Parallel Computing

by Michel Raynal
IRISA (Université de Rennes and INRIA)
France
raynal@irisa.fr

Abstract:

This talk will focuse on two communication modes, namely Logically Instantaneity (LI) and Causal Order (CO). These communication modes address two different levels of quality of service in message delivery. LI means that it is possible to timestamp communication events with integers in such a way that (1) timestamps increase within each process and (2) the sending and the delivery events associated with each message have the same timestamp. So, there is a logical time frame in which for each message, the send event and the corresponding delivery events occur simultaneously. CO means that, when a process delivers a message, its delivery occurs in a context where the receiving process knows all its causal past. Actually, LI is a property strictly stronger than CO.

The talk will present these noteworthy communication modes. Their main interest lies in the fact that they deeply simplify the design of message-passing programs that are intended to run on distributed memory parallel machines or cluster of workstations.

Keywords: Causal Order, Cluster of Workstations, Communication Protocol, Distributed Memory,Distributed Systems, Logical Time, Logical Instantaneity, Rendezvou


Last modified: Fri Jun 9 09:44:29 MET DST 2000