Parallelised branch-and-bound algorithm for raster-based landfill siting

Landfill siting analysis is complex when compactness and other factors are simultaneously evaluated. In our previous work, a raster-based mixed-integer model was proposed to overcome this difficulty, and a C program was further developed to improve the computational time for solving the raster-based model. In this study, an enhanced parallelised branch-and-bound algorithm was proposed to shorten the solving time further. A parallelised computing environment with five computers was established for implementing the proposed algorithm. For comparison purpose, the un-parallelised algorithm was also tested on a single computer. The results show that the parallelised algorithm and computing environment can increase the speed by about three to seven times, while compared to the original algorithm implemented on a single computer.