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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. 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

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  1. CS 470/570 Lecture 4 • Performance measures • Interconnection networks • Cache coherence • Parallel Software • Parallel Program design • Example Problems

  2. Performance Measures • Speedup • Tserial/Tparallel • Efficiency • Speedup/number of processors • Amdahl’s law • Scalable

  3. Interconnection Networks • Bus • Crossbar • Fully connected • Hypercube • Omega • Latency • Bandwidth

  4. Cache Coherence • Snooping cache coherence • Directory based cache coherence

  5. Parallel Software • Nondeterminism • Race conditions • Critical section • Mutual exclusion • Thread Safe

  6. Parallel Program Design • Partitioning • Communication • Aggregation

  7. 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?

  8. 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 How does Core 0 know its copy of the contents of address 10,000 is out of date.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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