Multiprocessor communication networks

A processor node in a parallel multiprocessor system, comprising:

• a processor generating messages to be sent simultaneously to a plurality of destination processor nodes over communication links in a packet-switching communication network, the processor dividing each message into a plurality of packets having a common destination processor node;
• an arbiter determining an order in which to forward the packets onto the packet-switching communication network toward their destination processor nodes, the arbiter substantially avoiding selecting two packets consecutively from any one of the messages when determining the order in which to forward the packets onto the packet-switching communication network;
• and
• a network interface sending the packets onto the network in accordance with the determined order, the determined order operating to substantially avoid sending consecutive packets from the processor node to a given destination processor node and to randomize the destination processor nodes of those packets presently traversing the communication network.

In a parallel multiprocessor system, a method for exchanging messages among processor nodes interconnected by a packet-switching communication network, the method comprising:

• identifying data to be sent simultaneously to a plurality of destination processor nodes;
• generating a message for each destination processor node of the plurality of destination processor nodes for carrying the data to that destination processor node;
• dividing each message into a plurality of packets having a common destination processor node;
• determining an order in which to forward the packets onto the communication network toward their destination processor nodes that substantially avoids sending consecutive packets from a given source processor node to a given destination processor node and randomizes the destination processor nodes of those packets presently traversing the communication network by substantially avoiding selecting two packets consecutively from any one of the messages when determining the order in which to forward the packets from that processor node onto the communication network.