The ECLiPSe Constraint Logic Programming System is designed for solving combinatorial optimization problems, for the development of new constraint solver technology and their hybrids, and for the teaching of modelling, solving and search techniques.
The Yap Prolog System is a ISO-compatible high-performance Prolog compiler. Yap is widely considered one of the fastest available Prolog systems. Yap supports coroutining, CLP(QR), CHR, and depth-bound search. Tabling and parallelism are in development.