This work presents the first extensive study of singlenode performance optimization, tuning, and analysis of the fast multipole method (FMM) on modern multicore systems. We consider single- and double-precision with numerous performance enhancements, including low-level tuning, numerical approximation, data structure transformations, OpenMP parallelization, and algorithmic tuning. Among our numerous findings, we show that optimization and parallelization can improve doubleprecision performance by 25 × on Intel’s quad-core Nehalem, 9.4 × on AMD’s quad-core Barcelona, and 37.6 × on Sun’s Victoria Falls (dual-sockets on all systems). We also compare our single-precision version against our prior state-of-the-art GPU-based code and show, surprisingly, that the most advanced multicore architecture (Nehalem) reaches parity in both performance and power efficiency with NVIDIA’s most advanced GPU architecture. 1

This paper throws a small “wet blanket ” on the hot topic of GPGPU acceleration, based on experience analyzing and tuning both multithreaded CPU and GPU implementations of three computations in scientific computing. These computations—(a) iterative sparse linear solvers; (b) sparse Cholesky factorization; and (c) the fast multipole method—exhibit complex behavior and vary in computational intensity and memory reference irregularity. In each case, algorithmic analysis and prior work might lead us to conclude that an idealized GPU can deliver better performance, but we find that for at least equal-effort CPU tuning and consideration of realistic workloads and calling-contexts, we can with two modern quad-core CPU sockets roughly match one or two