Space-efficient object models for object-oriented programming languages

• US 7,150,009 B2
• Filed: 12/10/2002
• Issued: 12/12/2006
• Est. Priority Date: 12/10/2002
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Bacon, David F., Grove, David P., Fink, Stephen J.
• Primary Examiner(s): Dam, Tuan
• Assistant Examiner(s): KENDALL, CHUCK O
• Application Number:
  US10/315,270
• Publication Number:
  US 20040111703A1
• Time in Patent Office: 1,463 Days
• Field of Search: 717127-131
• US Class Current: 717/127
• CPC Class Codes: G06F 9/4493 Object persistence

Abstract

A method for implementing an object model for an object-oriented programming language. Also contemplated is a method whereby some object state is materialized directly in those objects deemed likely to use such a state, but is externalized for those objects deemed unlikely to use the state.

Claims

1. A method of implementing an object model in an implementation of an object-oriented programming language, said method comprising the steps of:

predicting a set of objects that will use an object-specific instance of a given state during the lifetime of each object;

for each object predicted to use an object-specific instance of the given state, materializing a representation of the object-specific instance of the given state in a storage representation of the object;

providing an auxiliary data structure; and

for each object not predicted to use an object-specific instance of the given state;

upon the first attempted use of its object-specific instance of the given state, materializing the object-specific instance of the given state in the auxiliary data structure.

2. The method according to claim 1, wherein the auxiliary data structure is accessible via an indirect lookup mechanism.

3. The method according to claim 1, wherein said step of providing a auxiliary data structure comprises providing a nursery.

4. The method according to claim 3, wherein said step of providing a nursery comprises providing a hash table data structure which maps objects to states.

5. The method according to claim 4, further comprising the step of determining, via examining declared synchronization operations, whether an object will use locking.

6. The method according to claim 1, further comprising the step of evacuating the auxiliary data structure.

7. The method according to claim 6, wherein said evacuating step comprises:

for each unit of the object-specific instance of the given state in the nursery, moving the object-specific instance of the given state into the representation of the corresponding object; and

enabling subsequent direct access to the object-specific instance of the given state in the representation of the corresponding object.

8. The method according to claim 6, wherein the auxiliary data structure is evacuated during garbage collection.

9. The method according to claim 1, wherein predicting step comprises developing a prediction based on a declared type for each object.

10. The method according to claim 1, wherein the given state is representative of a per-object state related to locking.

11. The method according to claim 1, wherein the given state is representative of a per-object stare related to profiling.

12. The method according to claim 1, wherein said predicting step comprises, for at least one object, encoding the prediction as a bit in the representation of the object.

13. An apparatus which implements an object model in an implementation of an object-oriented programming language, said apparatus comprising:

a predictor which predicts a set of objects that will use an object-specific instance of a given state during the lifetime of each object;

a first materializer which, for each object predicted to use an object-specific instance of the given state, materializes a representation of the object-specific instance of the given state in a storage representation of the object;

an auxiliary data structure; and

a second materializer which, for each object not predicted to use an object-specific instance of the given state;

upon the first attempted use of its object-specific instance of the given state, materializes the object-specific instance of the given state in the auxiliary data structure.

14. The apparatus according to claim 13, wherein the auxiliary data structure is accessible via an indirect lookup mechanism.

15. The apparatus of claim 13, wherein said auxiliary data structure comprises a nursery.

16. The apparatus of claim 15, wherein said nursery comprises a hash table data structure which maps objects to states.

17. The apparatus of claim 13, further comprising an evacuator which evacuates the auxiliary data structure.

18. The apparatus of claim 17, wherein said evacuator, for each unit of the object-specific instance of the given state in the nursery,

moves the object-specific instance of the given state into the representation of the corresponding object;

and

enables subsequent direct access to the object-specific instance of the given state in the representation of the corresponding object.

19. The apparatus of claim 17, wherein the auxiliary data structure is evacuated during garbage collection.

20. The apparatus according to claim 13, wherein said predictor develops a prediction based on a declared type for each object.

21. The apparatus according to claim 13, wherein the given state is representative of a per-object state related to locking.

22. The apparatus of claim 16, further comprising a determiner which determines, via examining declared synchronization operations, whether an object will use locking.

23. The apparatus of claim 13, wherein the given state is representative of a per-object state related to profiling.

24. The apparatus of claim 13, wherein said predictor, for at least one object, encodes the prediction as a bit in the representation of the object.

25. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for implementing an object model in an implementation of an object-oriented programming language, said method comprising the steps of:

predicting a set of objects that will use an object-specific instance of a given state during the lifetime of each object;

for each object predicted to use an object-specific instance of the given state, materializing a representation of the object-specific instance of the given state in a storage representation of the object;

providing an auxiliary data structure; and

for each object not predicted to use an object-specific instance of the given state;

upon the first attempted use of its object-specific instance of the given state, materializing the object-specific instance of the given state in the auxiliary data structure.