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topologies. Using traces collected by our emulationbased techbetween any two nodes in one hop. To maintain simplicity, LL and
8 Interconnect Topologies Fall 2 nodes,
nique, we simulate application runs on hundreds of thousands of
LR links originating from only two013 numbered 0 and 16 are
cores. Nonuniform link bandwidths on different classes of links
shown in Figure 1 (left). Basic Topology requirements
For things to work
Must connect each processor to all others. i.e. it should be possible to send “messages” between any pair of processors
Must allow for physically viable arrangements (try arranging a star for thousands of processors)
The physically viable arrangement should be economically aﬀordable 9 Interconnect Topologies Fall 2013 Basic Topology requirements
For things to work well:
Intermediate rouBng, if needed, should happen without interfering with computaBon on intermediate nodes.
Reasonable path length between every pairs of processors
Easy to calculate path from one processor to other
More discussed later… 10 Interconnect Topologies Fall 2013 Topology Basic deﬁniBons
Let the topology be represented by a Graph G(V,E) where V is the set of verBces
processors/routers and E is the edges
connecBons among them degree: maximum number of edges incident on a vertex
distance between two verBces: number of edges (hops ) in shortest path between them
diameter: maximum distance between any pair of verBces
edge length : maximum physical length of any wire; may be constant or variable as number of processors varies
bandwidth
11 Interconnect Topologies Fall 2013 How to Judge a Topology
degree: aﬀects capability to communicate simultaneously
diameter: determines the maximum delay average...
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 Fall '08
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