Torus interconnect

Diagram of a 3 dimensional torus interconnect. It is not limited to 8 nodes but can consist of any number of nodes in a similar rectilinear array.

A torus interconnect is a network topology for connecting processing nodes in a parallel computer system. It can be visualized as a mesh interconnect with nodes arranged in a rectilinear array of N = 2, 3, or more dimensions, with processors connected to their nearest neighbors, and corresponding processors on opposite edges of the array connected.^[1] The lattice has the topology of an N dimensional torus and each node has 2N connections.

A number of supercomputers on the TOP500 list use three dimensional torus networks, e.g. IBM's Blue Gene/L and Blue Gene/P, and the Cray XT3.^[2] IBM's Blue Gene/Q uses a five dimensional torus network. Fujitsu's K computer and the PRIMEHPC FX10 use a proprietary six dimensional torus interconnect called Tofu.^[3]

Visualization

• In a two dimensional torus interconnect, the nodes are imagined laid out in a two dimensional rectangular lattice of rows and columns, with each node connected to its 4 nearest neighbors, and corresponding nodes on opposite edges connected. The connection of opposite edges can be visualized by rolling the rectangular array into a "tube" to connect two opposite edges and then bending the "tube" into a torus to connect the other two.
• In a three dimensional torus interconnect the nodes are imagined in a three dimensional lattice in the shape of a rectangular prism, with each node connected with its 6 neighbors, with corresponding nodes on opposing faces of the array connected.

Higher dimensional arrays can't be directly visualized, but each higher dimension adds another pair of nearest neighbor connections to each node.

See also

• Computer cluster
• Heartbeat private network
• Switched fabric

References