ASYNCHRONOUS AND DETERMINISTIC OBJECTS

1
ASYNCHRONOUS AND DETERMINISTIC OBJECTS
Denis CAROMEL, Ludovic HENRIO, Bernard Paul
SERPETTE

• ASP Asynchronous Sequential Processes
• Distributed objects
• Asynchronous method calls
• Futures and Wait-by-necessity
• Determinism properties

I3S - INRIA - Univ Nice Sophia-Antipolis
2
Context

• V-calculus
• Objects, not concurrent
• Some concurrent extensions, not our way to
  determinism
• ?-calculus
• Communications, channel based, not object
  structured
• Linear(ized) channels(pobl), no implicit
  synchronization
• Process Networks
• Processes, channel based, not object oriented
• Determinism, no implicit synchronization

Context
3
Contents

• 1 - ASP Principles
• 2 - Syntax and Semantics
• 3 - Confluence and Determinacy
• 4 - Conclusion

4
Structure
Active(a)
1- ASP Principles
5
Sending Requests ( REQUEST )
a
b
foo
beta.foo(b)
resultbeta.foo(b)
1- ASP Principles
6
Sending Requests ( REQUEST )
a
b
foo
beta.foo(b)
resultbeta.foo(b)
1- ASP Principles
7
Serving Requests ( SERVE )
a
b
Serve(foo)...
foo
beta.foo(b)
bar
Serve(foo)...
1- ASP Principles
8
Serving Requests ( SERVE )
a
b
Serve(foo)
beta.foo(b)
bar
Serve(foo)...
1- ASP Principles
9
End of Service ( ENDSERVICE )
a
b
value
...
foo
1- ASP Principles
10
End of Service ( ENDSERVICE )
a
b
...
foo
1- ASP Principles
11
Sending Results ( REPLY )
a
b
foo
1- ASP Principles
12
Sending Results ( REPLY )
a
b
foo
1- ASP Principles
13
Wait by Necessity
a
b
delta.send(result)
d
1- ASP Principles
14
Wait by Necessity
a
b
delta.send(result)
result.bar()
d
1- ASP Principles
15
Wait by Necessity
a
b
delta.send(result)
result.bar()
d
1- ASP Principles
16
Wait by Necessity
a
b
Futures updates can occur at any time
result.bar()
d
1- ASP Principles
17
Contents

• 1 - ASP Principles
• 2 - Syntax and Semantics
• 3 - Confluence and Determinacy
• 4 - Conclusion

18
ASP Syntax source terms

• Imperative V-calculus
• ASP parallelism primitives

2- Syntax and Semantics
19
Local
Creating Activity
Sending request
Receiving replies
2- Syntax and Semantics
20
Contents

• 1 - ASP Principles
• 2 - Syntax and Semantics
• 3 - Confluence and Determinacy
• 4 - Conclusion

21
Compatibility
Serves the oldest request on foo OR bar
bar
d
. Serve(foo,bar) Serve(foo,gee)
foo
gee
3- Confluence and Determinacy
22
Confluence

• Potential services

Execution characterized by the order of Request
Senders
Compatibility ? Confluence
3- Confluence and Determinacy
23
Deterministic Object Networks
g
b
d
foo,bar , foo,gee
bar,gee , foo
gee bar
bar gee
3- Confluence and Determinacy
24
Static DON
a
d
f
foo,bar , gee
gee, f,g
foo,bar , gee
f,g
g
g
g
foo
f
foo,bar , gee
foo, bar
bar
e
f
b
bar , gee
gee, f,g
gee, f,g
gee
3- Confluence and Determinacy
25
Contents

• 1 - ASP Principles
• 2 - Syntax and Semantics
• 3 - Confluence and Determinacy
• 4 - Conclusion

26
Conclusion

• An Asynchronous Object Calculus
• Structured asynchronous activities
• Structured communications with futures
• Data-driven synchronization
• ASP ? Confluence and Determinacy
• Future updates can occur at any time
• Execution characterized by the order of request
  senders
• Determinacy of programs communicating over trees,
  

Thank You Any Question?
4- Conclusion
27
Perspectives

• Approximation of confluence property
• Static analysis
• Generalization of confluence property
• Functional behavior
• Scheduling of requests
• Extensions of ASP
• Group communication
• Component calculus
• Mobility and other features

28
Related Work

• Futures and Wait by Necessity
• MultiLisp by Halstead
• Wait-By-Necessity by Caromel
• Determinism
• pobl by Jones, Linearized channels
• Process Networks by Kahn and MacQueen
• Objects and concurrency
• Obliq, Gordon-Hankin-Lassen
• Actors
• ?-calculus, blue calculus, join-calculus

29
Intermediate Structures

• Terms
• Configuration
• Request queue
• Futures list
• Store

30
Static DON versus Process Networks
a
d
f
foo,bar , gee
gee, f,g
foo,bar , gee
f,g
g
put
g
g
foo
f
foo,bar , gee
foo, bar
bar
e
f
b
get
bar , gee
gee, f,g
gee, f,g
gee
31
Activity Creation ( NEWACT )
a
Active(a)
b
newactActive(a)
32
Objects Topology
b
a
g
d
33
Equivalence Modulo Futures Updates
a
f1
b
g
f2
f3
34
More Futures
a
d
...
result.bar()
b
g
35
More Futures
a
d
result.bar()
b
g
36
More Futures
a
d
result.bar()
b
g
37
More Futures
a
d
result.bar()
b
g
38
More Futures
a
d
Futures updates can occur at any time
result.bar()
b
g
39
Concurrent Constraint Programming

• Constraint programming, different notion of store
• Shared memory
• No internal state in the store (functional agents)

• Data-driven / constraint driven synchronization
• Blocking Ask
• Determinate case

40
Activity Creation ( NEWACT )
a
Active(a,s)
newactActive(a,s)
41
Activity Creation ( NEWACT )
a
Active(a,s)
newactActive(a,s)
42
Equivalence Modulo Futures Updates
a
f1
b
g
f2
f3
43
Equivalence Modulo Futures Updates
a
a
f2
f1
b
g
b
g
f2
f3
44
Store Partitioning
45
Request Service ( SERVE )
b
Serve(foo)
bar
foo
Serve(foo)...
46
Request Service ( SERVE )
b
Serve(foo)
bar
foo
...
Serve(foo)...
47
Objectives

• Model of the following features
• Object orientation (activities, communications)
• Asynchronous communications with futures
• Service policy
• Confluence and determinacy
• Identify sources of non-determinism
• Characterize equivalent executions
• Give general properties
• Find some properties easy to verify

48
End Of Service ( ENDSERVICE )
b
value
foo
bar
...
49
End Of Service ( ENDSERVICE )
b
value
bar
foo
...
50
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