Affine Killing - TyDe'17

1. Affine Killing Kiko Fernandez-Reyes and Dave Clarke Uppsala University SCADA Funded by:
2. • Speculative, parallel abstractions: Problem • Easy to create parallelisation points • Hard to kill speculative computations (based on ParT)
3. Problem (based on ParT) Types
4. Problem { } { } (based on ParT) { _ } :: t → Par[t] Types
5. Problem { } { } (based on ParT) { _ } :: t → Par[t] >> :: Par[t] → (t → t’)→ Par[t’] Types >> λ >> λ λ = (fun social => findUser(social, user))
6. Problem { } { } parFb parTw (based on ParT) { _ } :: t → Par[t] >> :: Par[t] → (t → t’)→ Par[t’] Types >> λ >> λ λ = (fun social => findUser(social, user))
7. Problem || { } { } parFb parTw (based on ParT) { _ } :: t → Par[t] || :: Par[t] → Par[t] → Par[t] >> :: Par[t] → (t → t’)→ Par[t’] Types >> λ >> λ λ = (fun social => findUser(social, user))
8. Problem || phoneNumber << { } { } parFb parTw (based on ParT) { _ } :: t → Par[t] || :: Par[t] → Par[t] → Par[t] >> :: Par[t] → (t → t’)→ Par[t’] Types >> λ >> λ λ = (fun social => findUser(social, user)) ≪ :: (t → Par[t’]) → Par[t] → Par[t’]
9. Problem >> updateDB || phoneNumber << { } { } parFb parTw (based on ParT) { _ } :: t → Par[t] || :: Par[t] → Par[t] → Par[t] >> :: Par[t] → (t → t’)→ Par[t’] Types >> λ >> λ λ = (fun social => findUser(social, user)) ≪ :: (t → Par[t’]) → Par[t] → Par[t’]
10. Problem { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) (based on ParT)
11. Problem val parInf = parTw || parFb { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) (based on ParT)
12. Problem val parInf = parTw || parFb parTw >> updateDB { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) (based on ParT)
13. Problem getPhoneNumber ≪ parInf val parInf = parTw || parFb parTw >> updateDB { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) (based on ParT)
14. Problem getPhoneNumber ≪ parInf val parInf = parTw || parFb parTw >> updateDB { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) (based on ParT) Aliasing prevents killing unfinished computations
15. Problem getPhoneNumber ≪ parInf val parInf = parTw || parFb parTw >> updateDB { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) (based on ParT) When is it safe to kill computations? How to do it efficiently? Aliasing prevents killing unfinished computations
16. Solution 1. Kill using thread-local reasoning 2. Leverage static information from type system 3. No manual introduction of killing points 4. Integrated in the actor-based Encore language Limitation: Computations must be free of side effects
17. Outline • Problem • Affine type system • Solution
18. Affine type system val parInf = parTw || parFb { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) (parTw >> updateDB)
19. Affine type system val parInf = parTw || parFb { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) modes read ≊ shared lin ≊ affine fun findUser(social : lin Twitter, user : read User): read Info … end (parTw >> updateDB)
20. Affine type system val parInf = parTw || parFb { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) modes read ≊ shared lin ≊ affine fun findUser(social : lin Twitter, user : read User): read Info … end >> :: mode1 Par[mode2 t] → (mode2 t → mode2’ t’) → mode1’ Par[mode2’ t’] (parTw >> updateDB)
21. Affine type system val parInf = parTw || parFb { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) modes read ≊ shared lin ≊ affine fun findUser(social : lin Twitter, user : read User): read Info … end read Par[read Info] >> :: mode1 Par[mode2 t] → (mode2 t → mode2’ t’) → mode1’ Par[mode2’ t’] (parTw >> updateDB)
22. Affine type system val parInf = parTw || parFb { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) modes read ≊ shared lin ≊ affine fun findUser(social : lin Twitter, user : read User): read Info … end lin Par[read Info] read Par[read Info] >> :: mode1 Par[mode2 t] → (mode2 t → mode2’ t’) → mode1’ Par[mode2’ t’] (parTw >> updateDB)
23. Affine type system val parInf = parTw || parFb { } val parTw = >> (fun x => findUser(social, user)) { } val parFb = >> (fun x => findUserFb(social, user)) modes read ≊ shared lin ≊ affine fun findUser(social : lin Twitter, user : read User): read Info … end lin Par[read Info] read Par[read Info] lin Par[read Info] >> :: mode1 Par[mode2 t] → (mode2 t → mode2’ t’) → mode1’ Par[mode2’ t’] (parTw >> updateDB)
24. Outline • Problem • Affine type system • Solution
25. >> updateDB phoneNumber << parTw { }>> λ || parFb { }>> λ read linear Kill using thread-local reasoning
26. >> updateDB phoneNumber << parTw { }>> λ || parFb { }>> λ read linear Kill using thread-local reasoning
27. >> updateDB phoneNumber << parTw { }>> λ || parFb { }>> λ read linear Kill using thread-local reasoning parTw Information from Twitter available
28. >> updateDB phoneNumber << parTw { }>> λ || read linear Kill using thread-local reasoning parTw Information from Twitter available
29. >> updateDB phoneNumber << parTw { }>> λ || parFb { }>> λ read linear Kill using thread-local reasoning
30. >> updateDB phoneNumber << parTw { }>> λ || parFb { }>> λ read linear Kill using thread-local reasoning parFb Information from Facebook available
31. >> updateDB phoneNumber << parTw { }>> λ || parFb { }>> λ read linear Kill using thread-local reasoning parFb Information from Facebook available No operation
32. >> updateDB λ << >> λ || read Kill using thread-local reasoning linear linear || linear >> λ linear { } { }
33. >> updateDB λ << >> λ || read Kill using thread-local reasoning linear linear || linear >> λ linear { } { }
34. >> updateDB λ << >> λ || read Kill using thread-local reasoning linear || linear { }
35. val parInf = parTw || parFb lin Par[read Info] Leverage static information
36. || lin || lin v3 v4 || read v1 v2 parInf= val parInf = parTw || parFb lin Par[read Info] || parInst || parReddit Leverage static information
37. || lin || lin v3 v4 || read v1 v2 parInf= statically checked val parInf = parTw || parFb lin Par[read Info] || parInst || parReddit Leverage static information
38. || lin || lin v3 v4 || read v1 v2 parInf= statically checked labels change at runtime val parInf = parTw || parFb lin Par[read Info] || parInst || parReddit Leverage static information
39. || lin || lin v3 v4 || read v1 v2 parInf= statically checked labels change at runtime val parInf = parTw || parFb lin Par[read Info] || parInst || parReddit Leverage static information Translates into: - Reuse of ParT collection structure - Polymorphic dispatch
40. Leverage static information - Polymorphic dispatch ParT is statically checked, but the actual behaviour depends on the dynamic labels, which themselves may change
41. Leverage static information - Polymorphic dispatch ParT is statically checked, but the actual behaviour depends on the dynamic labels, which themselves may change
42. Leverage static information - Polymorphic dispatch ParT is statically checked, but the actual behaviour depends on the dynamic labels, which themselves may change
43. || lin || lin v3 v4 || read v1 v2 Sharing a linear reference parInf= parInf :: lin Par[read Info] Leverage static information
44. || lin || lin v3 v4 || read v1 v2 let !x = parInf in (!x >> λ) Sharing a linear reference parInf= parInf :: lin Par[read Info] Leverage static information
45. || lin || lin v3 v4 || read v1 v2 let !x = parInf in (!x >> λ) Sharing a linear reference parInf= parInf :: lin Par[read Info] !x :: read Par[read Info] !x = Leverage static information
46. || lin || lin v3 v4 || read v1 v2 let !x = parInf in (!x >> λ) Sharing a linear reference parInf= parInf :: lin Par[read Info] !x :: read Par[read Info] !x = read Leverage static information
47. || lin || lin v3 v4 || read v1 v2 let !x = parInf in (!x >> λ) Sharing a linear reference parInf= parInf :: lin Par[read Info] !x :: read Par[read Info] !x = read Leverage static information
48. || lin || lin v3 v4 || read v1 v2 let !x = parInf in (!x >> λ) Sharing a linear reference parInf= parInf :: lin Par[read Info] !x :: read Par[read Info] !x = read Leverage static information ParT is statically checked, but the actual behaviour depends on the dynamic labels, which themselves may change
49. || lin || lin v3 v4 || read v1 v2 let !x = parInf in (!x >> λ) Sharing a linear reference parInf= parInf :: lin Par[read Info] !x :: read Par[read Info] !x = read Leverage static information ParT is statically checked, but the actual behaviour depends on the dynamic labels, which themselves may change
50. Integration with Encore • Actor-based language • Capability-based type system linear subord active local Cannot escape its actor read Immutable No aliasing allowed Cannot escape its aggregate Actor, method calls return futures Restriction: A type has a single capability type
51. Integration with Encore • Actor-based language • Capability-based type system linear subord active local Cannot escape its actor read Immutable No aliasing allowed Cannot escape its aggregate Actor, method calls return futures Restriction: A type has a single capability type
52. Integration with Encore • Actor-based language • Capability-based type system linear subord active local Cannot escape its actor read Immutable No aliasing allowed Cannot escape its aggregate Actor, method calls return futures Restriction: A type has a single capability type
53. Integration with Encore • Actor-based language • Capability-based type system linear subord active local Cannot escape its actor read Immutable No aliasing allowed Cannot escape its aggregate Actor, method calls return futures Restriction: A type has a single capability type
54. Work in progress • How to kill: • Proof of soundness • Implementation • Guided by SAT solver and other benchmarks - Kill thread, actor or introduce well-defined stopping points - ParT internally relies on a task or actor running computations
55. Conclusion • Killing in an affine type system: • read (shared) references are nop • linear references can be killed • Thread-local reasoning when killing parallel computations • Leverage static information: e.g. polymorphic dispatch, in-place updates • Integration with Encore (status)