How Effective is Design Abstraction in Thrust?: An Empirical Evaluation

Ajai V. George, Sankar Manoj, Sanket R. Gupte, Santonu Sarkar

Abstract: High performance computing applications are far more difficult to write, therefore, practitioners expect a well-tuned software to last long and provide optimized performance even when the hardware is upgraded. It may also be necessary to write software using sufficient abstraction over the hardware so that it is capable of running on heterogeneous architecture. A good design abstraction paradigm strikes a balance between the abstraction and visibility over the hardware. This allows the programmer to write applications without having to understand the hardware nuances while exploiting the computing power optimally. In this paper we have analyzed the power of design abstraction of a popular design abstraction framework called Thrust both from ease of programming and performance perspectives. We have shown that while Thrust framework is good in describing an algorithm compared to the native CUDA or OpenMP version but it has quite a few design limitations. With respect to CUDA it does not provide any abstraction over the shared, texture or constant memory usage to the programmer. We have compared the performance of a Thrust application code in CUDA, OpenMP and the CPP backends with respect to the native versions (implementing exactly same algorithm), written for these backends and found that the current Thrust version performs poorly in most of the cases. While we conclude that the framework is not ready for writing applications that can exploit the optimal performance from the hardware, we also highlight the improvements necessary for the framework to make the performance comparable.