OpenCL vs: Accelerated Finite-Difference Digital Synthesis

Digital audio synthesis has become an important component of modern music production with techniques that can produce realistic simulations of real instruments. Physical modelling sound synthesis is a category of audio synthesis that uses mathematical models to emulate the physical phenomena of acoustic musical instruments including drum membranes, air columns and strings. The synthesis of physical phenomena can be expressed as discrete variants of Newton's laws of motion, using, for example, the Finite-Difference Time-Domain method or FDTD. FDTD is notoriously computationally expensive and the real time demands of sound synthesis in a live setting has led implementers to consider offloading to GPUs. In this paper we present multiple OpenCL implementations of FDTD for real time simulation of a drum membrane. Additionally, we compare against an AVX optimized CPU implementation and an OpenGL version that utilizes a careful mapping to the GPU texture cache. We find using a discrete, laptop class, AMD GPU that for all but the smallest mesh sizes, the OpenCL implementation out performs the others. Although, to our surprise we found that optimizing for work-group local memory provided only a small performance benefit.