Fast Collective Communication Libraries, Please

It has been recognized that many parallel numerical algorithms can be eeectively implemented by formulating the required communication as collective communications. Nonetheless, the eeciency of such communications has been suboptimal in many communication library implementations. In this paper, we give a brief overview of techniques that can be used to implement a high performance collective communication library, the iCC library, developed for the Intel family of parallel supercomputers as part of the InterCom project at the University of Texas at Austin. We compare the achieved performance on the Intel Paragon to those of three widely available libraries: Intel's NX collective communication library, the MPICH Message Passing Interface (MPI) implementation developed at Argonne and Mississippi State University and a Basic Linear Algebra Communication Subprograms (BLACS) implementation, developed at the University of Tennessee.