The Grid-Occam Project

1. The Grid-Occam Project Dipl.-Inf. Bernhard Rabe Dipl.-Inf. Peter Tröger Dr. Martin von Löwis Prof. Dr. rer. nat. habil. Andreas Polze Operating Systems & Middleware Group Hasso-Plattner-Institute, University of Potsdam

2. Outline • Introduction into Occam • The Grid-Occam Idea • The Grid-Occam lecture • Grid-Occam programs • Conclusions

3. Occam History • Based on Sir T. Hoare’s ideas of Communicating Sequential Processes (CSP) • Parallel processing language • Abstraction from underlying hardware, software and network environment • Developed by INMOS for transputer systems • Distributed memory system • 4 high-speed hardware links • Routing of messages for unconnected processors (virtual channel router)

4. Occam Language • Primitive actions • Variable assignment • Channel output • Channel input • SKIP • STOP • Sequential process combination (SEQ) • Parallel process combination (PAR) PROC hello() INT x,y: CHAN OF INT c,d: PAR SEQ c ! 117 d ? x SEQ c ? y d ! 118 :

5. ALT and Arrays • Alternative process combination (ALT) • Arrays ALT keyboard ? var1 to.computer ! var1 from.computer ? var1 screen ! var1 VALUE num.of.fields IS 500: [num.of.fields]REAL64 a,b: [num.of.fields]CHAN OF REAL64 c:

6. Rules in Occam • Rendezvous behavior of channels • Receiver blocks until the sender wrote the value • Sender continues after the receiver read the value • Variables can only be written by one process in parallel • Likewise, only a single process can read from a channel, and another single process can write to the channel

7. GridSphere CoG Execution Portal Grid Application Grid-Occam Cactus High-Level Grid Abstractions GridLab GAT GO Runtime Remote Procedure Call Control-Parallel Programming MessagePassing Grid RPC MPICH-G2 AMWAT WSRF Satin PACX MPI NetSolve Globus Grid Infrastructure (Resource Discovery, Job Execution, Intra/Inter-Node Communication) Unicore Building a Grid Application

8. The Grid-Occam Idea • Bring parallelism as first-level language construct to modern distributed environments • Consistent programming model for different granularities of distribution (threads, cluster nodes, grid nodes) • Support for heterogeneous execution platforms • .NET implementation on Rotor (MacOS X, Windows, FreeBSD) • Integration of legacy source code (e.g. Fortran) • Clear distinction of language compiler and infrastructure-dependent runtime library • Multithreaded runtime library • MPI runtime library • Grid runtime library • Support nested nature of granularity levels

9. Compiler and Libraries • Occam compiler • Generates C# code • Code utilizes common interface for all runtime library implementations • Multithreaded (MT) runtime library • Channels with interlocked shared memory, rendezvous behavior through multiple semaphore locks • Shared memory for global variables • .NET threads for parallel Occam processes • MPI runtime library • Minimal topology information (RANK, SIZE) • Fully interconnected node topology • Fine-granular parallel execution on one node by using the MT library • Rendezvous channels through synchronized send operation

10. Grid Runtime Library Idea • Grid-Occam as coordination language • External code represented as Occam procedure • Runtime library submits external executable to a grid resource • Usage of standard job submission API’s (DRMAA, GAT, COG) • Best-effort process placement • Utilize infrastructure information (e.g. MDS) • Consideration of channel bandwidth information (NWS) • (Partial) task graph generated by the compiler • Mapping algorithms from cluster research community • Distributed computation in the Grid • Based on Grid-enabled MPI (Mpich-G2) • Based on WSRF services (Occam channel service) • Proof of concept • Expose web services / WSRF services as Occam channel

11. Grid-Occam Execution Environment

12. The Accompanying Lecture • Run in Summer semester 2004 • 5 groups of 3-4 students • All groups produced .NET-based distributed runtime environments for Occam • Runtime environments • Support for SEQ, PAR, ALT • “Hello World” using 2 processes/2 channels as initial assignment • pthread-implementation of runtime was given to students • Compiler construction • Focus on tools: ANTLR, Coco/R, lex/yacc, kimwitu, • All compilers support a common Occam subset and different extensions

13. Translated into C# public class MainClass { [ProgramEntry] public static void _main5() { Occam.Channel _c_1 = new Occam.Channel(), _d_2 = new Occam.Channel(); int _x_3 = 0; Parallel0 parallel0 = (Parallel0)Runtime.CreateSequence(typeof(Parallel0 ), _x_3, _d_2, _c_1); int _y_4 = 0; Parallel1 parallel1 = (Parallel1)Runtime.CreateSequence(typeof(Parallel1 ), _y_4, _d_2, _c_1); Occam.Runtime.Parallel(parallel0, parallel1); parallel0.Result(out _x_3); parallel1.Result(out _y_4); } } } namespace Occam.UserCode{ public class Parallel0 : Occam.DistributedSequence { int _x_3; Occam.Channel _d_2; Occam.Channel _c_1; public Parallel0(int _x_3, Occam.Channel _d_2, Occam.Channel _c_1) { this._x_3 = _x_3; this._d_2 = _d_2; this._c_1 = _c_1; } public override void Run() { _c_1.Write((int)(117)); _x_3 = (int)_d_2.Read(); } public void Result(out int _x_3) { _x_3 = this._x_3; } } public class Parallel1 : Occam.DistributedSequence { … public override void Run() { _y_4 = (int)_c_1.Read(); _d_2.Write((int)(118)); } public void Result(out int _y_4) { _y_4 = this._y_4; } }

14. Translated into C# (2nd approach) public virtual void SEQ1() { WriteChannel c1__=cf.getWriteChannel("c1"); c1__.write(117); ReadChannel d1__=cf.getReadChannel("d2"); x3_ = ((System.Int32)d1__.read() ); } public virtual void SEQ2() { ReadChannel c2__=cf.getReadChannel("c1"); y4_ = ((System.Int32)c2__.read() ); WriteChannel d2__=cf.getWriteChannel("d2"); d2__.write(118); } [OccamMainProcess()] public virtual void PAR1() { ArrayList occamProcesses = new ArrayList(); occamProcesses.Add(new OccamProcess(SEQ1)); occamProcesses.Add(new OccamProcess(SEQ2)); env.execPAR(occamProcesses); } } } [OccamProgram()] public class MyOccamProgram { private IExecutionEnvironment env; private ChannelFactory cf; private IVariableStore vs; private int x3_; private int y4_; public MyOccamProgram(IExecutionEnvironment executionEnvironment) { env=executionEnvironment; cf=env.getChannelFactory(); } public MyOccamProgram(MyOccamProgram originalProcess) { env=originalProcess.env; cf=originalProcess.cf; x3_=originalProcess.x3_; y4_=originalProcess.y4_; } public static void Main(string[] args) { BootstrapLoader loader = new BootstrapLoader(args, Assembly.GetCallingAssembly()); }

15. Optimizing Datamanagement PROC hello() INT x,y: CHAN OF INT c,d: PAR SEQ c ! 117 d ? x SEQ c ? y d ! 118 : PROC hello() CHAN OF INT c,d: PAR INT x: SEQ c ! 117 d ? x INT y: SEQ c ? y d ! 118 :

16. Conclusions • First implementation of Occam in common intermediate language, and also the first implementation that implements Webservice channels in Occam. • Investigation of paradigms, design patterns and implementation techniques for enhancing middleware technology for predictable computing. • Linking grid computing and parallel computing techniques. • Teaching compiler construction, concurrent programming, (weakly consistent) distributed shared memory models.

17. Thank you, any questions ? http://www.dcl.hpi.uni-potsdam.de