The pre-detection algorithm, with the ability of parallel computation, can improve the efficiency of small target detection. Infrared ship detection with an attention mechanism focuses the limited computation resources on the interested region, though its computation task should be rightly divided to adapt the pipeline structure and parallel structure. Based on two start points: the balance between communication cost and parallel computation and the efficiency of utilizing the system resources, analysis has been made on the speedup performance of the algorithm, which provides a theoretical guidelines of the real-time realization of the algorithm.