Torus interconnect

A torus interconnect is a switch-less network topology for connecting processing nodes in a parallel computer system.

In geometry, a torus is created by revolving a circle about an axis coplanar to the circle. While this is a general definition in geometry, the topological properties of this type of shape describes the network topology in its essence.

The following images are 1D, and 2D torus. 1D torus is a simple circle, and 2D torus has the shape of doughnut. The animation below illustrates how a 2D torus is generated from a rectangle by connecting its two pairs of opposite edges. Here the concept of torus is used to describe essentially the beginning and ending of a sequence of nodes are connected, like a doughnut. To better illustrate the concept, and understand what the topology means in network interconnect, we give 3 examples of parallel interconnected nodes using torus topology. At one dimension, a torus topology is equivalent to a ring interconnect network, of a shape of a circle. At 2d, it’s equivalent to a 2D mesh, but with extra connection at the edge nodes, which is the definition of 2D torus.

1D torus example, a circle.

2D torus example, a donut.

Generating a 2D torus from a 2D rectangle.

We can generalize the rule from the figures above. Torus interconnect is a switch-less topology that can be seen 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] In this lattice, each node has 2N connections. This topology got the name from the fact that the lattice formed in this way is topologically homogeneous to an N-dimensional torus.

The first 3 dimensions of torus topology network are easier to visualize. Below are the description respectively.

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