设计MPI程序模拟广播（MPI_Bcast）操作：将每个MPI进程按照所在节点名称建立node通信子域分组；再将各个node子通信域的0号进程再次组成一个名为head的通信域；在进行广播时，首先由root进程将消息在head通信子域内广播，然后，再由head子域内各进程在其所在的node子域内进行广播。-MPI program design analog broadcast (MPI_Bcast) Action: Each MPI process to establish a communication node according to the node where the packet subdomain name　then process each node No. 0 sub-domain communication again form a communication domain named head　during broadcast , the first message in the head by a broadcast communication subdomain root process, and then again by the head of each sub-domain process in their broadcast node in the sub-region.