PaCCS was designed from the ground up with parallel execution on a network of multiprocessors in mind and exhibits good scalability on different systems. It features a hybrid implementation, using MPI and pthreads where a distinguished thread initiates the search, collects solutions,detects termination and returns answers. To achieve good load balancing, PaCCS implements work-stealing. When a search worker has covered its assigned search space, it then tries to obtain another search space from the other workers in the system.The idle worker first tries to obtain work from a worker
in its immediate neighbourhood, constituted by the workers in the same shared-memory system. Failing that, it gradually expands the neighbourhood considered until it encompasses the whole parallel search system. Work-stealing outside the worker’s immediate neighbourhood is done by proxy, and work requests with a common origin are aggregated.