1. Distributed Computing:
- not everything centralized
- many processors

2. Distributed Systems:
Internet
The machines of our department
ATM machines, bank accounts

3. What is then parallel computing?
Many processors in the same machine
All processors solve the same task
A restricted form of distributed computing

4. Basic Distributed Systems:
Message passing
Shared Memory

5. Message Passing Systems
Easy to implement in hardware

6. Shared Memory Systems
Harder to implement in hardware
Easy to program

7. Distributed Algorithms
Several problems:
Communication Problems
Coordination Problems
Specific problems

8. Example: The counting problem
Shared variable
Sequential Bottleneck!!!

9. A better solution:
Counting network
many shared
variables

10. Example: Routing Problems

11. Example: Finding the spanning tree problem

12. Example: Leader election problem

13. Example: Mutual Exclusion Problem
Critical Region
One processor allowed

14. Example: Consensus Problem
Time 0
Final Time 1 1 1 1 1 1 1 1 1

15. Topics:
Message Passing Model
Spanning Trees
Independent Set
Coloring
Clustering
Shared Memory
Mutual Exclusion
Byzantine Agreement
Consensus
Distributed Counting