1 / 24

Cilk NOW

Cilk NOW. Based on a paper by Robert D. Blumofe & Philip A. Lisiecki. Organization. Introduction The Cilk language & workstealing scheduler Cilk-NOW job architecture Adaptive parallelism Fault tolerance Cilk-NOW macro-scheduling Conclusion. Introduction: Cilk-NOW features. Ease of use

graham
Download Presentation

Cilk NOW

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cilk NOW Based on a paper by Robert D. Blumofe & Philip A. Lisiecki

  2. Organization • Introduction • The Cilk language & workstealing scheduler • Cilk-NOW job architecture • Adaptive parallelism • Fault tolerance • Cilk-NOW macro-scheduling • Conclusion

  3. Introduction: Cilk-NOW features • Ease of use Standard command line interface for running Cilk-NOW programs. • Adaptive parallelism Joining & retreating is oblivious to users. • Fault tolerance Cilk programs oblivious to: • Check-pointing • Failure detection & recovery

  4. Introduction: Cilk-NOW features … • Flexibility • Sovereignty of workstation’s owner is preserved: Owner defines “idle”. • Security • Customary Unix user security. Users must have Unix login on system. • Guaranteed performance Uses Cilk’s thread scheduler: • Work-stealing • Provably efficient  predictable performance.

  5. Introduction: Cilk-NOW features … • No distributed shared memory • No fault tolerance for I/O • All workstations share a file system. • Work focuses on: • Adaptive parallelism • Fault tolerance

  6. Organization • Introduction • The Cilk language & work-stealing scheduler • Cilk-NOW job architecture • Adaptive parallelism • Fault tolerance • Cilk-NOW macro-scheduling • Conclusion

  7. Cilk language & work stealing scheduler • This is the same as Cilk. • The standard Fibonacci example follows.

  8. Compute the nth Fibonacci Number thread fib ( cont int k, int n ) { if ( n < 2 ) send_argument ( k, n ); else { cont int x, y; spawn_next sum ( k, ?x, ?y ); spawn fib ( x, n – 1 ); spawn fib ( y, n – 2 ); } } thread sum ( cont int k, int x, int y ) { send_argument ( k, x + y ); }

  9. Organization • Introduction • The Cilk language & workstealing scheduler • Cilk-NOW job architecture • Adaptive parallelism • Fault tolerance • Cilk-NOW macro-scheduling • Conclusion

  10. Cilk-NOW job architecture • A Cilk-NOW job consists of: • A clearinghouse process • 1 or more worker processes • Begin a job by typing the command CilkChouse -- pfold 3 7 This starts a worker that: Forks a clearinghouse process that • Sends the job description to the macro-scheduler • Waits for messages from its workers.

  11. (b) An idle machine joins the job • Another machine’s node manager goes “idle” • It sends a job request to the macro-scheduler • The macro-scheduler returns the pfold job • The node manager forks a new worker with no associated clearinghouse • The worker registers with the pfold clearinghouse • The clearinghouse gives the worker: • Its name (worker names are integers, starting from 0) • A list of other workers on this job • The worker steals a closure from a worker.

  12. (c) A no-longer idle machine retreats • The machine’s owner touches the keyboard • Node manager sends kill signal to its worker • Worker catches signal: • Offloads closures to other workers • Un-registers from clearinghouse • Terminates

  13. Maintaining the work lists • Each worker checks in with clearinghouse every 2 seconds. If a worker’s “lease” expires ( no check in for 30 sec.) then the clearinghouse removes it from its list • Clearinghouse returns a list of revisions: • workers to add & delete from local list.

  14. UDP • UDP between: • Workers • Clearinghouse & worker • Faster than TCP for the common case. • No pretense of reliability when none exists.

  15. Organization • Introduction • The Cilk language & workstealing scheduler • Cilk-NOW job architecture • Adaptive parallelism • Fault tolerance • Cilk-NOW macro-scheduling • Conclusion

  16. Adaptive parallelism • What happens when a waiting closure gets offloaded to another worker? • How do send_argument invocations get their info to the moved waiting closure? • The paper describes a notion of sub-computation, and uses this notion to handle this situation. • To be continued …

  17. A simple way ? • Have the waiting closure’s unfilled arguments refer to the continuations that refer to them. • When the waiting closure is offloaded to a new worker, the waiting closure informs its continuations of its new address. • For this to work, when a continuation is passed to another closure, the waiting closure is informed • This may be a lot of work. • To be continued …

  18. Organization • Introduction • The Cilk language & workstealing scheduler • Cilk-NOW job architecture • Adaptive parallelism • Fault tolerance • Cilk-NOW macro-scheduling • Conclusion

  19. Fault tolerance • To be continued, based on a fuller understanding of closure migration under worker retreat.

  20. Organization • Introduction • The Cilk language & workstealing scheduler • Cilk-NOW job architecture • Adaptive parallelism • Fault tolerance • Cilk-NOW macro-scheduling • Conclusion

  21. Cilk-NOW macro-scheduling

  22. Organization • Introduction • The Cilk language & workstealing scheduler • Cilk-NOW job architecture • Adaptive parallelism • Fault tolerance • Cilk-NOW macro-scheduling • Conclusion

More Related