Abstract: The aim of our research is to develop the optimal task scheduling algorithm that minimizes the computing period in general network structures considering communication contention and routing delay. We present new ideas of scheduling: i) the individual start that allows overlapping two different iterations, ii) the scheduling space and the scheduling graph that represent feasible schedules, and iii) the check-and-diffusion algorithm utilizing property of the start-time difference vs. the computing period. With concrete examples of scheduling spaces, segments, and schedules, we show that individual start reduces the computing period, and our algorithm can find the optimal start-time difference.