UWICL: A multi-layered parallel image computing library for single-chip multiprocessor-based time-critical systems

Many software libraries have been created to support the commonly used primitive operations needed in image processing, image analysis and image understanding. Generally, these libraries are based on the single-layered Application Program Interface (API). While a single-layered API provides the useful abstraction level to interact with the library and hides unnecessary implementation details from the user, it does not produce an efficient program when a new algorithm is implemented by assembling the selected existing library routines. The composed program suffers from the inefficient data movement and additional loop control overhead. Furthermore, when a system employs a highly integrated processor such as a single-chip multiprocessor, the single-layered API prevents the user from fully utilizing the resources available in the system. In this article, we describe the University of Washington Image Computing Library (UWICL), the multi-layered high-performance parallel image computing library for Texas Instruments TMS320C80 Multimedia Video Processor (MVP)-based time-critical systems. Our goal in designing the UWICL is to provide the TMS320C80 user community with efficient and flexible image computing library routines. The UWICL provides three levels of APIs to the programmers under the multi-layered organization, the MVP-level API, the DSP-level API, and APIs for data flow and processing cores. By optimizing the processing core functions, we have achieved high performance in the individual function level, and by allowing the sub-primitive library routine composition, we can achieve efficient image processing application development, avoiding most problems encountered in using the single-layered library routines. The performance of the multi-layered organization vs. the single-layered one is analysed and compared using the Canny's edge detection algorithm as an example. The balanced composition based on the multi-layered organization outperforms the single-layered composition by 14 to 41% depending on the system's memory bandwidth available. As an adjunct to the UWICL, we have also developed an integrated MVP performance monitor (MPM). The MPM can identify the performance bottleneck of the TMS320C80 applications and can be used in optimization by enabling the user to select the most efficient library composition level in building the application with the UWICL. In order to provide the overall performance evaluation model of the MVP, the simple MVP functional model has also been defined in the MPM. For the image thresholding operation, the difference between the measured execution time and the analysis prediction is less than 2%, The design and implementation of the MPM, and the applicability and usefulness of the MPM and MVP performance model are described in this article. (C) 1996 Academic Press Limited