Performance of MPI broadcast algorithms

As cluster computing has gotten cheaper and more powerful, ever larger clusters are being built and ever larger problems are being tackled. Many, if not most, of these problems require the broadcast of data not only at the beginning of the computation but also as it progresses. Given the comparative slowness of communication as opposed to computation, any improvement in communication time can have a significant impact on the time required to complete a computation. This paper looks at the broadcast function of MPI and explores some alternative implementations for the common cluster architecture in which some number of computing nodes are connected via an Ethernet switch. It then compares these implementations to the built-in implementation of broadcast in MPICH2 and suggests a new implementation.