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1 Typed Groups for the Grid Laurent Baduel
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Typed Groupsfor the Grid
Laurent Baduel
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Outline
Context and Objectives Typed groups Application: Jem3D Object-Oriented SPMD Group extensions and usage Conclusion and Perspectives
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Introduction
Traditional uses of group communicationFault tolerance, ReplicationApplicative groups, Parallelism
Our objectives: Applicative groupsEfficient communicationCollaborative applicationsEasy structuringObject-oriented programming
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Analysis of related works 3 projects close to our concerns:
JGroups Centered on low layers of communication Socket programming style
Object Group Service CORBA focused Group communication return only one result (by default)
Group Method Invocation Group members have to implement and extend a
class and an interface
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Analysis of related works
Lack of transparency Specific interface for functional calls Inheritance from specific classes and
interfaces Sometimes too application/domain-specific
We want to address those problems !
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Communication model
RMI + important new featuresActive object:
A single thread serves requests with a FIFO service
Asynchronous method call Rendez-vous Transparent futures
Wait-by-necessity Automatic wait upon a strict operation on a future First class futures
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JVMJVM
Active objectA a = PA.newActive(“A”, […], VirtualNode);V v1 = a.foo (param);V v2 = a.bar (param);…
v1.gee();
a barv1v2 foo
Javaobject
Activeobject
Requestqueue
Future Thread
// Wait-By-Necessity
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Context and Objectives Typed groups Application: Jem3D Object-Oriented SPMD Group extensions and usage Conclusion and Perspectives
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Typed group communications
Idea / goalManipulate groups as “plain” Java objectsMaintain the dot notationCode reusability
Creation of a typed groupGroup members have a common type ancestor
public class A { … }A ag = (A) ProActiveG.newGroup(“A”, params, node);
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Group communications
Remote method invocation on a group Multi-unicast approach
Replication of N single communicationsBased on the standard communication
mechanismEach communication is adapted to the calleeAdapt the rendez-vous to group communicationsAdapt the Wait-by-Necessity mechanism
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Result of a group communication
Result is dynamically built and updatedV vg = ag.foo();
Immediately operablevg.gee();
Rank property Synchronization primitiveProActiveGroup.waitOne(vg);
ProActiveGroup.waitAll(vg);
Object o = ProActiveGroup.waitAndGetOne(vg);
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Group call
JVM
JVM
JVM
JVM
agvg
A ag = PAG.newGroup(“A”,…,vn);V vg = ag.foo(param);…
vg.gee();…
// Wait-By-Necessity
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Two representations
Management operations: add, remove, etc.
Two representations of a same groupTyped group (type of the members)
Group of objects (extends Collection)
Ability to switch between themGroup groupA = ProActive.getGroup(ag);
groupA.add(new A());groupA.add(new B()); // B extends A
A ag2 = (A) groupA.getTypedGroup();
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Two representations schema
Managementof the group
Functional use of the group
Group of objectsgroupA
getGroupstatic method of class ProActive
getTypedGroupmethod of class Group
Typed groupgA
Single JavaRepresentation
(Transparent) (Explicit)
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Broadcast or scatter
Broadcast is the default behavior Scatter is also possible
Scatter uses a group as parameterDistribution relies on rank
ag.bar(cg); // broadcast cg
ProActive.setScatterGroup(cg);
ag.bar(cg); // scatter cg
One call may scatter and broadcast
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Broadcast or scatter
JVM
JVM
JVM
JVM
agcg
ag.bar(cg); // broadcast cgProActive.setScatterGroup(cg);ag.bar(cg); // scatter cg
c1 c2c3c1 c2c3
c1 c2c3c1 c2c3
c1 c2c3
c1 c2c3
s
c1 c2c3
s
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Static Dispatch Group
JVM
JVM
JVM
JVM
agcg
c1
c2
c3
c4
c5
c6
c7
c8c0
c9c1
c2
c3
c4
c5
c6
c7
c8c0
c9
c1
c2
c3
c4
c5
c6
c7
c8c0
c9
Slowest
Fastestemptyqueue
ag.bar(cg);
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Dynamic Dispatch Group
JVM
JVM
JVM
JVM
agcg
c1
c2
c3
c4
c5
c6
c7
c8c0
c9c1
c2
c3
c4
c5
c6
c7
c8c0
c9
c1
c2
c3
c4
c5
c6
c7
c8c0
c9
Slowest
Fastest
ag.bar(cg);
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Performances and Optimizations Common operation
Single reificationSingle serialization
Parallel calls (adaptive thread pool)
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Error management Using Java exceptions
Common way to express failure in Java A group may produce several exceptions
during one communication Result group is used to store exceptions The ExceptionList is an exception that
contains raised exceptions associated with a reference to the object that produced them
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Error interception
JVM
JVM
JVM
JVM
agvg
V vg = ag.foo (param);Group groupV = PAG.getGroup(vg);groupV.getExceptionList();vg.gee();
failure
Except.
Except.List
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Active and hierarchical groups
Active group: a group serviceA group becomes remotely accessibleModifiable service policy
Hierarchical groupA group of groupsDynamically builtAchieves scalability
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grid frontal
cluster
clusterclustercluster
Grid deployment
Asynchronous callSynchronous call
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Grid method calls Grid’5000
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Context and Objectives Typed groups Application: Jem3D Object-Oriented SPMD Group extensions and usage Conclusion and Perspectives
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Jem3D Translation of a FORTRAN application:
EM3D Solves 3D Maxwell equations Relies on finite volume approximation
method Works on unstructured tetrahedral
discretization of the computation domain
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Communication based on groups
Groups allow sub-domains communication
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Algorithm of Jem3D
Initialization
Compute mag. field, and update elec. field
Compute elec. field, and update mag. field
Calculation of the discreteelectromagnetic energy
Solution Saving
t < tmax
t = tmax
Intensive group communications
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Jem3D
Computation of the propagation of an electromagnetic wave in a cubic metallic cavity (standard test case)
INRIA Sophia’s clusterDAS-2
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Context and Objectives Typed groups Application: Jem3D Object-Oriented SPMD Group extensions and usage Conclusion and Perspectives
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Main MPI problems for the Grid
Too static in design Too complex interface (API)
More than 200 primitives and 80 constants Too many specific primitives to be adaptive
Send, Bsend, Rsend, Ssend, Ibsend, etc. Typeless (message passing)
Manual management of complex data structures
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Object-Oriented SPMD
MotivationCluster / Grid programmingSPMD programming widely used
Already able to express most of the MPI’s collective communicationsBroadcastScatter
Different barriers Topologies
Gather Reduce
(Single Program Multiple Data)
All scatterAll gather
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JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
SPMD group CreationA ag = ProActive.newSPMDGroup(“A”, … );
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SPMD Group
SPMD Group is a typed group where members get:Local reference to the SPMD group they
belongs toMembershipAccess to their rank
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Topologies
Topologies are groups of objectsPlan plan = new Plan(groupSPMD, dimensions); Open API
Neighborhood Creation by extractionLine line = plan.getLine(0);
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The Jacobi iterations example
Solve a linear system of equations Typical SPMD program Algorithm loops on:
Exchange dataWait for dataComputeLoop (until exit condition is satisfied)
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Jacobi algorithm
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
2 5 7 9 1 0 1 0 5 6 7 8 ……
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Global barrier Involves all group membersProActive.barrier(“barrierID”);
JVM
JVMJVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
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Neighbor-based barrier Involves only the caller and its neighborsProActive.barrier(“barrierID”, neighbors);
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
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Method-based barrier Involves only the caller (no additional messages)
ProActive.barrier({“foo”, “bar”, “gee”});
JVM
JVMJVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
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OO SPMD model
A simple communication modelSmall APINo explicit receive: data flow synchronizationNo message passing: asynchronous RPCComplex data structures (Objects)
SPMD groups are dynamicDedicated barriersTopologies
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Context and Objectives Typed groups Application: Jem3D Object-Oriented SPMD Group extensions and usage Conclusion and Perspectives
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Group behavior manager
Definition of a group behaviorRequest mappingParameters distributionResults gatheringSynchronization semantic
Dynamic configuration and binding IP Multicast library
Bindings to multicast transport protocolTRAM, included in JRMS 1.1
In collaboration with University of Sannio – Benevento (Italy)
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Groups in the component framework Implementation of the Fractal component model Collective ports Composite components
Typed group
At binding,on client interface
At composition,on composite inner server interface
Typed groupParallel Component
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Context and Objectives Typed groups Application: Jem3D Object-Oriented SPMD Group extensions and usage Conclusion and Perspectives
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Conclusion High level, Efficient, Transparent, Typed
Group CommunicationNo dedicated inheritance requirementDynamic handling of resultsHigh level synchronization
Tested with a real size application Object-Oriented model for SPMD
ProgrammingMore flexibleEasier to use
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Perspectives
Exception handling Improvement of the adaptive thread pool Integrate other group semantics MxN redistribution for components Further development of the OO SPMD
model
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Thank you for your attention
? ? ? Questions ? ? ?
