ObjectOriented SPMD

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Object-Oriented SPMD
Laurent Baduel, Denis Caromel, Françoise Baude
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Context Objectives

• Traditional use of group communication
• Fault tolerance, replication, database
• Applicative groups, parallelism
• Our objectives
• Collaborative applications
• More efficient communication
• Simplicity and easy structuring
• Object-oriented programming

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Communication model

• Java RMI new important features
• Sequential Object
• a single thread with FIFO service
• Asynchronous method call
• rendez-vous
• Futures
• Wait-by-Necessity
• Automatic wait upon a strict operation on a
  future
• First class futures
• Futures can be passed to other activities
• Sending a future to another machines is not
  blocking

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Active Object
A ag PA.newActive (A, , VirtualNode) V v1
ag.foo (param) V v2 ag.bar
(param) ... v1.gee() //Wait-By-Necessity
Wait-By-Necessity is a Dataflow Synchronization
JVM
ag
Req. Queue
Java Object
Active Object
Future Object
Thread
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Typed group communication

• Idea / Goals
• Manipulate groups as plain Java objects
• Maintain the dot notation
• Code reusability
• Creation of typed group
• Group members have a common type ancestor

public class A A gA ProActive.newGroup(A
, params, nodes)
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Group communication

• Remote method invocation on a group
• Multi-unicast approach
• Based on the ProActive communication mechanism
• Replication of N single communication
• Each communication is adapted
• Preserve the rendez-vous

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Group the result of aGroup Communication

• Result are dynamically built and updated
• B groupB groupA.foo()
• Ranking order property
• Synchronization primitive
• ProActive.waitOne(gb)
• ProActive.waitAll(gb)

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Construction of a result group
B groupB groupA.foo()
A
Java object
Java object
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Two representations

• Management operations add, remove,
• 2 representations (views) of a same group
• Typed group
• Group of object
• Ability to switch between those 2 views

Group groupA ProActive.getGroup(gA) groupA.add(
new A()) groupA.add(new B()) // B herits from
A A gA2 (A) groupA.getGroupByType()
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Broadcast or scatter

• Broadcast is the default behavior
• Scatter is also possible
• use a group as parameter
• Scattered depends on rankings
• gA.bar(gC) // broadcast gC
• ProActive.setScatterGroup(gC)
• ga.bar(gC) // scatter gC
• One call may scatter and broadcast

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Features of groups

• Optimization
• Parallel calls within a group (adaptive
  threadpool)
• Treatment in the result return order
• Single serialization
• Flexibility Active group
• A group becomes remotely accessible
• Modifiable service policy

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Main MPI problems for the GRID

• Too static in design
• Too complex in Interface (API)
• Too many specific primitives to be adaptive
• Type Less

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Object-Oriented SPMD

• Motivation
• Cluster / GRID computing
• SPMD programming notoriety
• Able to express most of MPIs collective
  communications
• broadcast
• scatter
• gather
• Different barriers

• reduce
• allscatter
• allgather

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SPMD group

• Creation
• A ag ProActive.newSPMDGroup(A,...)

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Topologies

• Topologies are typed groups
• Open API
• Neighborhood
• Creation by extraction

Plan plan new Plan(groupA, Dimensions) Line
line plan.getLine(0)
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The Jacobi Iteration example

• Solve a linear system of equations
• Typical SPMD program
• Algorithm loop on
• exchange data
• wait for the data
• compute
• loop (until exit condition is satisfied)

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Global barrier

• Involves all group member
• ProActive.barrier(barrierID)

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Neighbor-based barrier

• Involves only the caller and it neighbors
• ProActive.barrier(barrierID,neighbors)

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Method-based Barrier

• Involves only the caller
• no additional messages
• ProActive.barrier(foo,bar,gee)

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ProActive OO SPMD

• A simple communication model
• Small API
• No Receive but data flow synchronization
• No message passing but RPC
• Complex data structure (Object)
• SPMD groups are dynamic
• Efficient and dedicated barrier

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? ? ? Questions ? ? ?
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Two representations
Management of the group
Functional use of the group
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Group communication is now a key feature of
ProActive

• Used in many applications and other features

Chat
Jem3D
Peer to peer
Multiport component
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Common operation factorization
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Thread pool
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Hierarchical groups

• Group contains groups
• Add a typed group into a group
• Benefit of the network structure

A
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