Split-C and Active Messages David E. Culler Computer Science Division U.C. Berkeley The first part of this talk will present Split-C, a simple parallel extension to C for engineering parallel programs on distributed memory machines. Split-C provides the programmer with a global address space, yet maintains a clear cost model and a distinction between local and global access. This allows sophisticated global data structures to be represented explicitly in the program, rather than being implicit in the communication pattern. It provides a simple framework in which to minimize the number of remote references and retains the ability to run highly-tuned sequential code within a processors local portion of the address space. The language provides an unusual set of assignment operators to allow communication to be optimized. These capture important advantages of message passing and data parallel execution that traditional shared memory models forsake and further blur the distinctions between these models. Split-C is one of several parallel languages implemented on top of Active Messages. The second part of the talk will discuss Active Messages, a fast, flexible communication primitive, and their implementation on the nCUBE and the CM-5. This should lead to an interesting discussion on the capabilities of Paragon under such a communication model.