1 / 49

Multiple Ownership

Multiple Ownership. Nicholas Cameron Sophia Drossopoulou James Noble Matthew Smith. Background – Ownership Types Multiple Ownership Objects in Boxes Variance - ? MOJO Effects. Background. Ownership Types. The heap is messy:. Ownership Types. Organise it:. Ownership Types.

arnie
Download Presentation

Multiple Ownership

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. Multiple Ownership Nicholas CameronSophia DrossopoulouJames NobleMatthew Smith

  2. Background – Ownership Types • Multiple Ownership • Objects in Boxes • Variance - ? • MOJO • Effects ncameron@doc.ic.ac.uk

  3. Background ncameron@doc.ic.ac.uk

  4. Ownership Types • The heap is messy: ncameron@doc.ic.ac.uk

  5. Ownership Types • Organise it: ncameron@doc.ic.ac.uk

  6. Ownership Types • Give each object an owner: ncameron@doc.ic.ac.uk

  7. Ownership Types class Project<o> { Task<this> t1; Task<this> t2; List<this, o> clients; } ncameron@doc.ic.ac.uk

  8. Our Work ncameron@doc.ic.ac.uk

  9. The Objects In Boxes Model ncameron@doc.ic.ac.uk

  10. A Box is a Set of Objects ncameron@doc.ic.ac.uk

  11. Objects in Boxes • Single owner interpretation: • An object is in its owner’s box ncameron@doc.ic.ac.uk

  12. Programs are not Trees ncameron@doc.ic.ac.uk

  13. One Owner is not Enough • 75% of ownership structures require multiple ownership • [34] Mitchell, ECOOP, ’06 • Trees can not describe non-hierarchical structures ncameron@doc.ic.ac.uk

  14. Objects in Boxes • Multiple Ownership: objects may be in more than one box • An object with multiple owners is in the intersection of their boxes: ncameron@doc.ic.ac.uk

  15. Objects in Boxes ncameron@doc.ic.ac.uk

  16. A Descriptive System • Describes the heap • Does not restrict references etc. ncameron@doc.ic.ac.uk

  17. MOJO ncameron@doc.ic.ac.uk

  18. MOJO • Class declarations have the usual, formal ownership parameters: class C<o, d> … ncameron@doc.ic.ac.uk

  19. MOJO • Class declarations have the usual, formal ownership parameters: class C<o, d> … • Types may have multiple corresponding actual owner parameters: C<b, c> ncameron@doc.ic.ac.uk

  20. MOJO • Class declarations have the usual, formal ownership parameters: class C<o, d> … • Types may have multiple corresponding actual owner parameters: C<b, c> C<a & b, c> ncameron@doc.ic.ac.uk

  21. MOJO • Class declarations have the usual, formal ownership parameters: class C<o, d> … • Types may have multiple corresponding actual owner parameters: C<b, c> C<a & b, c> C<a & b & ?, c & a> ncameron@doc.ic.ac.uk

  22. MOJO class Connection<o> { … } class Client<o, s> { Connection<this & s> c; } class Server<o> { Connection<this & ?> c; } ncameron@doc.ic.ac.uk

  23. Variance ncameron@doc.ic.ac.uk

  24. Variance • Connection<this & ?> • Some owner ncameron@doc.ic.ac.uk

  25. Variance • Connection<this & ?> • Some box • May be the intersection of several boxes • Variance in the number of owners ncameron@doc.ic.ac.uk

  26. Subtyping • Subtyping with wildcards is variant with respect to owners: C<a> <: C<?> ncameron@doc.ic.ac.uk

  27. Subtyping • Subtyping with wildcards is variant with respect to owners: C<a> <: C<?> C<a> <: C<a & ?> ncameron@doc.ic.ac.uk

  28. Subtyping • Subtyping with wildcards is variant with respect to owners: C<a> <: C<?> C<a> <: C<a & ?> C<a & b & ?> <: C<a & ?> ncameron@doc.ic.ac.uk

  29. Subtyping • Subtyping with wildcards is variant with respect to owners: C<a> <: C<?> C<a> <: C<a & ?> C<a & b & ?> <: C<a & ?> C<?> </: C<a> C<a> </: C<a & b> ncameron@doc.ic.ac.uk

  30. Constraints class C<a, b, c> a intersects b, b disjoint c { … } ncameron@doc.ic.ac.uk

  31. Constraints class D<a, b> a intersects b { D<a, b>  } class E<a, b> a disjoint b { } ncameron@doc.ic.ac.uk

  32. Constraints class D<a, b> a intersects b { D<a, b>  } class E<a, b> a disjoint b { D<a, b>  } ncameron@doc.ic.ac.uk

  33. Constraints class D<a, b> a intersects b { D<a, b>  Object<a & b>  } class E<a, b> a disjoint b { D<a, b>  } ncameron@doc.ic.ac.uk

  34. Typing - strict • Strict method sends and assignments to deal with variance of owners: class C<o> { C<o> f; } C<a> ca; C<a & ?> c1; C<a & ?> c2; ca.f = ca;  ncameron@doc.ic.ac.uk

  35. Typing - strict • Strict method sends and assignments to deal with variance of owners: class C<o> { C<o> f; } C<a> ca; C<a & ?> c1; C<a & ?> c2; ca.f = ca;  c1.f = c2;  ncameron@doc.ic.ac.uk

  36. Typing - strict ncameron@doc.ic.ac.uk

  37. Effects ncameron@doc.ic.ac.uk

  38. Effects ncameron@doc.ic.ac.uk

  39. Effects Task<x> t1; Task<y> t2; … t1.f; // reads x / writes ε ncameron@doc.ic.ac.uk

  40. Effects Task<x> t1; Task<y> t2; … t1.f; // reads x / writes ε t1.f = t2.f; // reads x,y / writes x ncameron@doc.ic.ac.uk

  41. Effects with Multiple Owners Task<x & ?> t1; Task<y & z> t2; … t1.f; // reads x & ? / writes ε ncameron@doc.ic.ac.uk

  42. Effects with Multiple Owners Task<x & ?> t1; Task<y & z> t2; … t1.f; // reads x & ? / writes ε t1.f = t2.f; // reads x & ?,y & z/ writes x & ? ncameron@doc.ic.ac.uk

  43. Effects with Multiple Owners t1.f = t2.f; // reads x & ?,y & z/ writes x & ? ncameron@doc.ic.ac.uk

  44. Disjointness • Two expressions are disjoint if their effects do not overlap • Complicated by ? – but & = intersection ncameron@doc.ic.ac.uk

  45. Future Work ncameron@doc.ic.ac.uk

  46. Future Work • Explore variant owners using existential types class TaskList<o, d> { Task<d & ?> datum; TaskList<o, d> next; } ncameron@doc.ic.ac.uk

  47. Future Work • Reference and modification control ncameron@doc.ic.ac.uk

  48. Future Work • Constraints • Topology - inside • Unary - may read, may write • Binary – may point to, may modify ncameron@doc.ic.ac.uk

  49. Summary • Ownership Types • Multiple Ownership • Objects in Boxes • Variance • MOJO • Effects • Thank you! • Any questions? ncameron@doc.ic.ac.uk

More Related