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Parallel and Distributed Processing CSE 8380

Parallel and Distributed Processing CSE 8380. April 14, 2005 Session 25. Contents. Project Update Quick review Communication Patterns Client/Server Systems Clusters. Switching Mechanism. Advantages. Disadvantages. Circuit Switching. Suitable for long messages Deadlock-free.

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Parallel and Distributed Processing CSE 8380

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  1. Parallel and Distributed ProcessingCSE 8380 April 14, 2005 Session 25

  2. Contents • Project Update • Quick review • Communication Patterns • Client/Server Systems • Clusters

  3. Switching Mechanism Advantages Disadvantages Circuit Switching Suitable for long messages Deadlock-free Wasting of Bandwidth Packet Switching Simple Suitable for interactive traffic Bandwidth on demand Buffer for every packet Potential long latency Potential deadlock Virtual Cut-Through Good for long messages Possible deadlock avoidance Elimination of data-link protocol Need for multiple message buffers Wasting of bandwidth Mainly used with profitable routing Wormhole Good for long messages Reduced need for buffering Reduced effect of path length Possibility for deadlock Inability to support backtracking Switching Techniques

  4. Message, Packets, Flits Message Packet Destination Sequence Data flit

  5. Latency Analysis • L  packet length (in bits) • W  Channel bandwidth (bits/sec) • D  Distance (number of hops) • F  flit length (in bits)

  6. Store and Forward Latency D

  7. WH Latency D

  8. Latency Analysis • L  packet length (in bits) • W  Channel bandwidth (bits/sec) • D  Distance (number of hops) • F  flit length (in bits) • TSF = D * L/W • TWH = L/W + D* F/W  L/Wif L>>F (independent of D)

  9. Communication Patterns • Point to Point  1 - 1 • Multicast  1 - n • Broadcast  1 - all • Conference  n - n

  10. Routing Efficiency • Two Parameters • Channel Traffic (number of channels used to deliver the message involved) • Communication Latency (distance)

  11. Multicast on a mesh (5 unicasts) Traffic ? Latency ?

  12. Multicast on a mesh (multicast pattern 1) Traffic ? Latency ?

  13. Multicast on a mesh (multicast pattern 2) Traffic ? Latency ?

  14. Broadcast (tree structure) 3 2 3 4 2 1 2 3 1 1 2

  15. Message Passing in PVM (Revisit) Sending Task Receiving Task User application Library User application Library 5 1 4 8 6 2 3 7 Daemon Daemon

  16. Client Client Server Server Threads Interconnection Network Client/Server Systems

  17. Server 1 Server 2 Server 3 Server n Slaves (Workers) Interconnection Network Client Master (Supervisor) A Client Server Framework for Parallel Applications

  18. Programming Environment and Tools Middleware Interconnection Network OS OS OS M M M I/O I/O I/O C C C P P P Clusters

  19. Interconnection Network Data Rate Switching Routing Ethernet 10 Mbit/sec Packet Table-based Fast Ethernet 100 Mbit/sec Packet Table-based Gigabit Ethernet 1 Gbit/sec Packet Table-based Myrinet 1.28 Gbit/sec wormhole Source-path Quadrics 7.2 Gbyte/sec wormhole Source-path Interconnection Networks in Clusters

  20. Port 4 Port 0 5 0 6 Port 5 Port 1 Port 6 Port 2 Port 7 Port 3 id 6 Dest-id Port 4 Port 0 Port 5 Port 1 Port 6 Port 2 Port 7 Port 3 Routing table Source-Path versus Table Based

  21. Thank you

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