This paper describes Accelerator, a system that simplifies the programming of GPUs for general-purpose uses. Accelerator provides a high-level data-parallel programming model as a library that is available from a conventional imperative programming language (C#). The library translates the data-parallel operations on-the-fly to optimized GPU pixel shader code and API calls. The authors describe the compilation techniques used to produce optimized pixel shader code, and demonstrate the effectiveness of the approach by providing results for a set of compute-intensive benchmarks drawn from image processing and computer vision. The speeds of the Accelerator versions of the benchmarks are typically within 50% of the speeds of hand-written pixel shader code. Some benchmarks significantly outperform C versions running on a CPU by up to 18x. (Accelerator: simplified programming of graphics processing units for general-purpose uses via data-parallelism David Tarditi, Sidd Puri, Jose Oglesby. Microsoft Research Technical Report MSR-TR-2005-184. December 2005.)