Abstmct-The use of adaptive routing in a multicomputer interconnection network improves network performance by making use of all available paths and provides fault tolerance by allowing messages to be routed around failed channels and nodes. This paper describes two deadlock-free adaptive routing algorithms. Both algorithms allocate virtual channels using a count of the number of dimension reversals a packet has performed to eliminate cycles in resource dependency graphs. The s t d c algorithm

more »

... liminates cycles in the network channel dependency graph. The dynamic algorithm improves virtual channel utilization by permitting dependency cycles and instead eliminating cycles in the packet wail-for graph. We prove that these algorithms are deadlock-free and give experimental measurements of their performance. For nonuniform traffic patterns, these algorithms improve network throughput by a factor of three compared to deterministic routing. The dynamic algorithm gives better performance at moderate traffic rates but requires source throttling to remain stable at high traffic rates. Both algorithms allow the network to gracefully degrade in the presence of faulty channels.