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A b s t r a c t. The Cell Broadband Engine™ is a heterogeneous multi-core architecture developed by IBM, Sony and Toshiba. It has eight computation intensive cores (SPEs) with a small local memory, and a single PowerPC core. The SPEs have a total peak single precision performance of 204.8 Gflops/s, and 14.64 Gflops/s in double precision. Therefore, the Cell has a good potential for high performance computing. But the unconventional architecture makes it difficult to program. We propose an implementation of the core features of MPI as a solution to this problem. This can enable a large class of existing applications to be ported to the Cell. Our MPI implementation attains bandwidth up to 6.01 GB/s, and latency as small as 0.41 µs. The significance of our work is in demonstrating the effectiveness of intra-Cell MPI, consequently enabling the porting of MPI applications to the Cell with minimal effort.

The Cell Broadband Engine TM is a new heterogeneous multi-core processor from IBM, Sony, and Toshiba. It contains eight coprocessors, called Synergistic Processing Elements (SPEs), which operate directly on distinct 256 KB local stores, and also have access to a shared 512 MB to 2 GB main memory. The combined peak speed of the SPEs is 204.8 Gflop/s in single precision and 14.64 Gflop/s in double precision. There is, therefore, much interest in using the Cell BE TM for high performance computing applications. However, the unconventional architecture of the SPEs, in particular their local stores, creates some programming challenges. We describe our implementation of certain core features of MPI, such as blocking point-to-point calls and collective communication calls, which can help meet these challenges, by enabling a large class of MPI applications to be ported to the Cell BE TM processor. This implementation views each SPE as a node for an MPI process. We store the application data in main memory in order to avoid being limited by the local store size. The local store is abstracted in the library and thus hidden from the application with respect to MPI calls. We have achieved bandwidth up to 6.01 GB/s and latency as low as 0.41 μs on the ping-pong test. The contribution of this work lies in (i) demonstrating that the Cell BE TM has good potential for running intra-Cell BE TM MPI applications, (ii) enabling such applications to be ported to the Cell BE TM with minimal effort, and (iii) evaluating the performance impact of different design choices.