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# CS 470/570 Lecture 4 PowerPoint PPT Presentation

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.

CS 470/570 Lecture 4

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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

• Tserial/Tparallel

• Efficiency

• Speedup/number of processors

• Amdahl’s law

• Scalable

### Interconnection Networks

• Bus

• Crossbar

• Fully connected

• Hypercube

• Omega

• Latency

• Bandwidth

### Cache Coherence

• Snooping cache coherence

• Directory based cache coherence

### Parallel Software

• Nondeterminism

• Race conditions

• Critical section

• Mutual exclusion

### Parallel Program Design

• Partitioning

• Communication

• Aggregation

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 How does Core 0 know its copy of the contents of address 10,000 is out of date.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