An efficient parallel interval narrowing algorithm for solving numerical problems is designed,
implemented and tested. Differences with the corresponding sequential algorithm are clearly
stated. The algorithm's performance is analyzed in the Bulk-Synchronous Parallel (BSP) cost
model which suggests speed-ups on high-bandwidth architectures. Experimental results on
a massively parallel machine Cray T3E-1200 validate the model and show the parallel
algorithm's efficiency as well as its limitations.