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CS 470/570 Lecture 4. Performance measures Interconnection networks Cache coherence Parallel Software Parallel Program design Example Problems. Performance Measures. Speedup T serial /T parallel Efficiency Speedup/number of processors Amdahl’s law Scalable. Interconnection Networks.

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Cs 470 570 lecture 4
CS 470/570 Lecture 4

  • Performance measures

  • Interconnection networks

  • Cache coherence

  • Parallel Software

  • Parallel Program design

  • Example Problems


Performance measures
Performance Measures

  • Speedup

    • Tserial/Tparallel

  • Efficiency

    • Speedup/number of processors

  • Amdahl’s law

  • Scalable


Interconnection networks
Interconnection Networks

  • Bus

  • Crossbar

  • Fully connected

  • Hypercube

  • Omega

  • Latency

  • Bandwidth


Cache coherence
Cache Coherence

  • Snooping cache coherence

  • Directory based cache coherence


Parallel software
Parallel Software

  • Nondeterminism

    • Race conditions

    • Critical section

    • Mutual exclusion

  • Thread Safe


Parallel program design
Parallel Program Design

  • Partitioning

  • Communication

  • Aggregation


Example problems
Example Problems

  • 1. Draw a 4X4 crossbar switch.

  • 2. Draw a 4X4 Omega network

  • 3. Suppose there are 16 processors connected in a 4 dimensional hypercube.

    • a. How many direct connections to other processors does each processor have?

    • b. What is the minimum number of links that will have to be traversed to send data from processor 3 to processor 12?


Example problems1
Example Problems

  • 4. Suppose you have a machine with 4 cores that uses snooping cache coherence. Core 0 reads from address 10,000, core 3 reads from address 10,000. Core 3 writes to address 10,000. How does Core 0 know its copy of the contents of address 10,000 is out of date.

  • 5. On a 4X4 Omega network can the following source destination requests be satisfied at the same time. (0,0), (3,1), (1,2), (2,3)

  • 6. How many switches are in an 8X8 crossbar?

  • 7. How many switches are on an 8X8 Omega network?


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