1. Challenges in Concurrent Computing
Danny Hendler

2. סמינר מצטיינים, 20 למאי 2012

3. Moore’s law Exponential growth in computing power
סמינר מצטיינים, 20 למאי 2012

4. The Future of Computing
Speeding up uni-processors is harder and harder
Intel, Sun (RIP), AMD, IBM now focusing on “multi-core” architectures
Already, multiprocessors are everywhere:
Desktops
Laptop
Smart phones
Smart TVs
...?
How can programmers write correct, efficient and scalable algorithms for multiprocessors?
סמינר מצטיינים, 20 למאי 2012

5. סמינר מצטיינים, 20 למאי 2012

6. Synchronization alternatives: coarse-grained locks
Pros
Easy to program
Cons
Sequential
סמינר מצטיינים, 20 למאי 2012

7. Synchronization alternatives: fine-grained locks
Pros
Potentially scalable
Cons
Difficult to program correctly
Deadlock
Priority inversion
Convoying
Locks do not compose
סמינר מצטיינים, 20 למאי 2012

8. Synchronization alternatives: nonblocking synchronization
Various progress guarantees
Wait-freedom,
Lock-freedom
Obstruction-freedom
Generally requires strong synchronization
compare-and-swap
Load-link/store-conditional
Swap, fetch-and-add
Pros
Potentially scalable
Avoids lock-based hazards
Cons
Extremely difficult to program
סמינר מצטיינים, 20 למאי 2012

9. Synchronization alternatives: Transactional Memory
A (memory) transaction is a sequence of memory reads and writes executed by a single thread that either commits or aborts
If a transaction commits, all the reads and writes appear to have executed atomically
If a transaction aborts, none of its operations take effect
Transaction operations aren't visible until they commit (if they do)
To be supported soon in hardware by Intel and IBM processors
סמינר מצטיינים, 20 למאי 2012

10. סמינר מצטיינים, 20 למאי 2012

11. Talk outline Introduction
Non-blocking algorithms (separate presentation)
Randomized mutual exclusion (separate presentation)
Research directions
סמינר מצטיינים, 20 למאי 2012

12. Talk outline Introduction
Non-blocking algorithms (separate presentation)
Randomized mutual exclusion (separate presentation)
Research directions
סמינר מצטיינים, 20 למאי 2012

13. Talk outline Introduction
Non-blocking algorithms (separate presentation)
Randomized mutual exclusion (separate presentation)
Research directions
סמינר מצטיינים, 20 למאי 2012

14. Research directions: practical
Devising efficient implementations of transactional memory
Includes incorporating OS kernel support
Devising efficient and scalable lock-based and non- blocking data structures
Some find their way to Java libraries
Devising algorithms that use few barrier instructions
...
סמינר מצטיינים, 20 למאי 2012

15. Research directions: theoretical
Lower bounds and impossibility results on deterministic and randomized mutual exclusion
Lower bounds and impossibility results on concurrent data-structures' (counters, stacks, queues, ...) complexity according to various metrics.
Formulating novel realistic metrics for concurrent algorithms and corresponding upper/lower bounds
סמינר מצטיינים, 20 למאי 2012

16. סמינר מצטיינים, 20 למאי 2012