a parallel computer system which divides the entire space of facilities into a plurality of small divisions ; assigns a plurality of processors thereof to the divisions , respectively , the lower stream processors receiving data on a boundary condition from the upper stream processor by communication to determine a condition for the continuity of the adjacent divisions , the processors carrying out parallel analytical operations for the analysis of the data on the corresponding divisions so as to meet the received boundary condition ; and collects data obtained by the parallel analytical operations of the processors in a host computer to obtain analytical data on the large - scale facilities . the lower stream processors assigned to the lower stream divisions receive boundary conditions provided by the upper stream processors assigned to the upper stream divisions in order starting from the lowermost stream processor assigned to the lowermost steam division upward , and the processor to receive data gives a data transmission request signal to the processor to transmit data , and the latter processor transmits data to the former processor after receiving the data transmission request signal given thereto by the former processor .