Compiling CHR to parallel hardware

This paper investigates the compilation of a committed-choice rule- based language, Constraint Handling Rules (CHR), to specialized hardware circuits. The developed hardware is able to turn the intrin- sic concurrency of the language into parallelism. Rules are applied by a custom executor that handles constraints according to the best degree of parallelism the implemented CHR specification can of- fer. Our framework deploys the target digital circuits through the Field Programmable Gate Array (FPGA) technology, by first com- piling the CHR code fragment into a low level hardware description language. We also discuss the realization of a hybrid CHR inter- preter, consisting of a software component running on a general purpose processor, coupled with a hardware accelerator. The latter unburdens the processor by executing in parallel the most computa- tional intensive CHR rules directly compiled in hardware. Finally the performance of a prototype system is evaluated by time effi- ciency measures.