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Challenges in Concurrent Computing

Challenges in Concurrent Computing. Danny Hendler. Moore’s law Exponential growth in computing power. 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:

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Challenges in Concurrent Computing

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  1. Challenges in Concurrent Computing Danny Hendler

  2. סמינר מצטיינים, 20 למאי 2012

  3. Moore’s lawExponential 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

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