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Static Connection Networks

• Trees: degree k, depth d, N=k^d-1 nodes.
  • Degree: K+1.
  • Diameter: 2(d-1) approx.2log _k N
  • Bisection width: 1! (hot spot!)
  • Edge length: not constant.
  • Root becomes communication bottleneck.
• Fat Tree
  • "Branches get thicker toward the root".
  • Channel width increases toward the root.
  • Communication bottleneck is avoided.
  • Example: Connection Machine CM-5.

Fat trees are also popular topologies.