Functional programming on a dataflow architecture: Applications in real-time image processing

This paper presents a dataflow functional computer (DFFC) developed at the Etablissement Technique Central de l'Armement (ETCA) and dedicated to real-time image processing. Two types of data-driven processing elements, dedicated respectively to low-level and mid-level processings are integrated in a regular 3D array. The design of the DFFC relies on a close integration of the dataflow-architecture principles and the functional programming concept. An image processing algorithm, expressed with a syntax similar to that of functional programming (FP) is first converted into a dataflow graph. The nodes of this graph are real-time operators that can be implemented on the physical processors of the dataflow machine. This dataflow graph is then mapped directly onto the processor array. The programming environment includes a complete compilation stream from the FP specification to hardware implementation, along with a global operator database. Apart from being a research tool for real-time image processing, the DFFC may also be used to perform the automatic synthesis of autonomous vision automata from a high-level functional specification. An experimental system, including 1024 lowlevel custom dataflow processors and 12 T800 transputers, was built and can perform up to 50 billion operations/s. Several image processing algorithms were implemented on this system and run in real-time at digital video speed.