Concurrent Revisions

A Scala implementation of the “Concurrent Programming with Revisions and Isolation Types” paper.

Presented at the North East Scala Symposium, New York NY, 2014 http://nescala.org/

Transcript

1. Concurrent Revisions Daniel W. H. James @dwhjames
2. This is not the Akka talk you were looking for…
3. What if your program could be concurrent in the same way that you use git?
4. research.microsoft.com/ en-us/projects/revisions Disclosure: not my work!
5. Sebastian Burckhardt, Alexandro Baldassion, and Daan Leijen. Concurrent Programming with Revisions and Isolation Types. In Proceedings of the ACM International Conference on Object Oriented Programming Systems Languages and Applications (OOPSLA’10), ACM SIGPLAN, Reno, NV, October 2010 Daan Leijen, Sebastian Burckhardt, and Manuel Fahndrich. Prettier Concurrency: Purely Functional Concurrent Revisions. In Haskell Symposium 2011 (Haskell’11), ACM SIGPLAN, Tokyo, Japan, 7 July 2011 Disclosure: not my work!
6. val v = VersionedValue(0) isolation type ->
7. val v = VersionedValue(0)
8. val v = VersionedValue(0) val r = Revision.fork { assert(v.value === 0) v.value = 1 }
9. val v = VersionedValue(0) val r = Revision.fork { assert(v.value === 0) v.value = 1 } assert(v.value === 0)
10. val v = VersionedValue(0) val r = Revision.fork { assert(v.value === 0) v.value = 1 } assert(v.value === 0) Revision.join(r) assert(v.value === 1)
11. val v = VersionedValue(0) val r = Revision.fork { assert(v.value === 0) v.value = 1 }
12. val v = VersionedValue(0) val r = Revision.fork { assert(v.value === 0) v.value = 1 } v.value = 2
13. val v = VersionedValue(0) val r = Revision.fork { assert(v.value === 0) v.value = 1 } v.value = 2 assert(v.value === 2)
14. val v = VersionedValue(0) val r = Revision.fork { assert(v.value === 0) v.value = 1 } v.value = 2 assert(v.value === 2) Revision.join(r) assert(v.value === 1)
15. git merge -X theirs myRev
16. val v = CumulativeValue(1, addMerge) isolation type -> merge fn ->
17. val v = CumulativeValue(1, addMerge)
18. val v = CumulativeValue(1, addMerge) val r = Revision.fork { assert(v.value === 1) v.value += 2 }
19. val v = CumulativeValue(1, addMerge) val r = Revision.fork { assert(v.value === 1) v.value += 2 } v.value += 3
20. val v = CumulativeValue(1, addMerge) val r = Revision.fork { assert(v.value === 1) v.value += 2 } v.value += 3 assert(v.value === 4)
21. val v = CumulativeValue(1, addMerge) val r = Revision.fork { assert(v.value === 1) v.value += 2 } v.value += 3 assert(v.value === 4) Revision.join(r) assert(v.value === 6)
22. val addMerge = (root: Int, main: Int, join: Int) => main + join - root
23. v = 1 v += 2 v += 3 assert(v === 6)
24. val x = VersionedValue(0) val y = VersionedValue(0) val r = Revision.fork { if (x.value == 0) y.value += 1 } if (y.value == 0) x.value += 1 Revision.join(r) assert(x.value === ???) assert(y.value === ???)
25. x = 0 y = 0 if(y==0) x++ assert(???) if(x==0) y++
26. x = 0 y = 0 if(y==0) x++ assert((x==0 && y==1) || (x==1 && y==0) || (x==1 && y==1)) if(x==0) y++ sequential consistency
27. x = 0 y = 0 lock.synchronized { if(y==0) x++ } assert((x==0 && y==1) || (x==1 && y==0)) lock.synchronized { if(x==0) y++ } mutex lock
28. x = 0 y = 0 atomic { if(y==0) x++ } assert((x==0 && y==1) || (x==1 && y==0)) atomic { if(x==0) y++ } transactional memory
29. x = 0 y = 0 if(y==0) x++ assert(x==1 && y==1) if(x==0) y++ concurrent revisions
30. github.com/dwhjames/ scala-concurrent-revisions
31. Demo!