Supporting Sets of Arbitrary Connections on iWarp
                   through Communication Context Switches

        Anja Feldmann        Thomas M. Stricker        Thomas E. Warfel

                         School of Computer Science
                         Carnegie Mellon University
                       Pittsburgh, Pennsylvania 15213
                                                                       
In this paper we introduce the ConSet communication model for distributed
memory parallel computers. The communication needs of an application program
can be satisfied by some arbitrary set of connections which are partitioned
into discrete phases. A communication context switch is used to select the
active phase.

We present an implementation of the ConSet model on the iWarp and describe its
performance characteristics, contrasting it to a message passing implementation
on the same machine. Our implementation demonstrates how one existing parallel
computer can function as a "reconfigurable network" without needing a new
processor interconnect technology.
                                                                       
The ConSet model works best when communication patterns can be optimized at
compile time. We examine the interactions of the target architecture with the
algorithmic problems encountered designing a communication compiler to
effectively partition, route, and schedule connections. We built a prototype
communication compiler for our iWarp implementation, and are using it to
generate iWarp code. Looking at basic communication patterns as well as
patterns generated by an iterative finite element PDE solver, we compare
ConSet's performance (using the compiler's schedules) to that of message
passing. Our experiments suggest that ConSet com- munication offers a
performance advantage over message passing in applications where the
communication pattern is known at compile time.


Proceedings of the Fifth ACM Symposium on Parallel Algorithms and
Architectures (Schloss Velen, Westfalia, Germany), pages 203-212, ACM,
July 1993.  PostScript (240k).


Paper available by anonymous FTP to WARP.CS.CMU.EDU in directory quake-papers/
as the file spaa93-arbitrary-connection-sets.ps, or through the URL
http://www.cs.cmu.edu/~quake-papers/spaa93-arbitrary-connection-sets.ps


BibTeX entry:

@inproceedings{feldmann93,
author = {Anja Feldmann and Thomas M. Stricker and Thomas E. Warfel},
title = {Supporting {S}ets of {A}rbitrary {C}onnections on i{W}arp through
  {C}ommunication {C}ontext {S}witches},
booktitle = {Fifth Annual Symposium on Parallel Algorithms and Architectures},
address = {Schloss Velen, Westfalia, Germany},
publisher = {Association for Computing Machinery},
pages = {203--212},
month = jul,
year = 1993,
ISBN = {0-89791-599-2},
}