Communication in Multiprocessor Systems

1
Communication in Multiprocessor Systems

• Presented by Thanh Thuy Ho

2
Communication in Multiprocessor Systems

• Fixed Connections
• Reconfigurable Connections
• Routing on Multistage Interconnection Networks

3
Fixed Connections

• Clustering has processors
• Cluster bus to connect processors
• Intercluster gateway handles data transfers
• between clusters. These gateways are connected
  by
• an intercluster communications mechanism.

4
(No Transcript)
5

• Reconfigurable Connection
• Crossbar switch
• Crosspoint to connect the input
• and output.
• Drawback is size.
• An n x m crossbar switch

6
Reconfigurable Connections

• Multistage Interconnection Networks (MINs) to
  connect input and output
• Routing algorithm is used to set the switches of
  a MINS

7
Nonblocking network

• It can realize any of the n! connections.
• Strictly nonblocking
• If a network can modify one connection without
  changing any others
• Rearrangeably nonblocking
• If a network can realize a new connection, but
  may have to reroute the path used to realize an
  existing connection in order to do so.
• Clos network
• Beneš network

8
Clos network designed for telephone switching
systems
9
Clos network

• Nn?k inputs
• Three stages
• If m?n , the network is rearrangeably
  nonblocking.
• If m?2n-1 , the network is strictly nonblocking.
• Hardware complexity O(n lg n) O(n2)

10
Beneš network was derrived from Clos
network by setting nm2 and k N/2
recursively decomposing the two (N/2)?(N/2)
switches. Hardware complexity O(n lg n)An 8
x 8 Beneš network
11
Blocking network

• (a)Omega network
• Hardware complexity O(n lg n)
• 12 switches
• (b)Baseline network
• It is essentially the front half of a Beneš
  network.
• 
  These two networks are isomorphic

12
Routing on Multistage Interconnection Networks

• Looping algorithm centralized algorithm O(n lg
  n)
• Recursive method used to set the switches of a
  Beneš network.
• p(s1) (0,0) (1,1) (2,3) (3,2) (4,5) (5,4)
  (6,6) (7,7)
• L1 (0,0) (1,4) (2,1) (3,5) (4,2)
  (5,6) (6,3) (7,7)
• p(s1) x L1 (0,0) (1,4) (2,5) (3,1) (4,6) (5,2)
  (6,3) (7,7)
• Ex. To realize (0,1) (1,2) (2,3) (3,4) (4,5)
  (5,6) (6,7) (7,0)
• Set stage1(1) 0,0) (1,1) ? straight
• Send i/p 0 ? upper subnetwork ? stage5 must be
  set to exchange o/p 0 received from lower subnet
  ? i/p 7 switch ? straight ? upper subnet
  (0,1)(2,3)(4,5)(6,7)
• lower subnet
  (1,2)(3,4)(5,6)(7,0)

13
Result of Looping Algorithm(a)after one
iteration (b)final results
14
Routing on multistage interconnection networks

• Omega network distributed , self routing
  procedure.
• 1st stage switch upper o/p ? E,G ? I,J ?
  0,1,2,3
• lower o/p ?
  F,H ?K,L ? 4,5,6,7
• 2nd stage switch upper o/p ? I,K ? 0,1,4,5
• lower o/p ?
  J,L ? 2,3,6,7
• Ex. (0,7)(1,3)(2,1)(3,6)(4,0)(5,5)(6,2)(7,4)
  successful
• (0,4)(1,0)(2,5)(3,3)(4,7)(5,1)(6,2)(7,6)
  blocked at 2nd stage

15
(a)successful and (b) unsuccessful routing on the
Omega network
16
The End

• Thank you