Vodca view oriented distributed cluster based approach to parallel computing
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VODCA: View-Oriented, Distributed, Cluster-based Approach to parallel computing. Dr Zhiyi Huang Dept of Computer Science University of Otago New Zealand. Motivation. DSM applications are not as efficient as MPI on cluster computers. VOPP.

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VODCA: View-Oriented, Distributed, Cluster-based Approach to parallel computing

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Vodca view oriented distributed cluster based approach to parallel computing

VODCA: View-Oriented, Distributed, Cluster-based Approach to parallel computing

Dr Zhiyi Huang

Dept of Computer Science

University of Otago

New Zealand

Zhiyi’s RSL


Motivation

Motivation

  • DSM applications are not as efficient as MPI on cluster computers

Zhiyi’s RSL


Vodca view oriented distributed cluster based approach to parallel computing

VOPP

  • VODCA is a system supporting View-Oriented Parallel Programming (VOPP)

  • Why a new programming style?

    • Improve the performance of DSM applications on cluster computers

    • Provide a programming style better than MPI

      • Message passing is notoriously known as a difficult programming style

Zhiyi’s RSL


What is a view

What is a view?

  • Suppose M is the set of data objects in shared memory

  • A view is a group of data objects from the shared memory

    •  V, VM

  • Views must not overlap each other

    •  Vi, Vj, i  j, Vi  Vj = 

  • Suppose there are n views in shared memory

    • ∑ Vi=M

Zhiyi’s RSL


Vopp requirements

VOPP Requirements

  • The programmer should divide the shared data into a number of views according to the data flow of the parallel algorithm.

  • A view should consist of data objects that are always processed as an atomic set in a program.

  • Views can be created and destroyed anytime.

  • Each view has a unique view identifier

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Vopp requirements cont

VOPP Requirements (cont.)

  • View primitives such as acquire_view and release_view must be used when a view is accessed.

    acquire_view(View_A);

    A = A + 1;

    release_view(View_A);

  • acquire_Rview and release_Rview can be used when a view is only read by a processor.

Zhiyi’s RSL


Example

Example

  • A VOPP program for a producer/consumer problem

If(prod_id == 0){

acquire_view(1);

produce(x);

release_view(1);

}

barrier(0);

acquire_Rview(1);

consume(x);

release_Rview(1);

Zhiyi’s RSL


Advantages of vopp

Advantages of VOPP

  • Keep the convenience of shared memory programming

  • Focus on data partitioning and data access instead of data race and mutual exclusion

    • View primitives automatically achieve mutual exclusion

    • View primitives are not extra burden

  • The programmer can finely tune the parallel algorithm by careful view partitioning

Zhiyi’s RSL


Philosophy of vopp

Philosophy of VOPP

  • Shared memory is a critical resource that needs to be used with care

    • If there is no need to use shared memory, don’t use it

    • Justification is wanted before a view is created

Zhiyi’s RSL


Vopp vs mpi

VOPP vs. MPI

  • Easier for programmers than MPI

    • For problems like task queue, programming with MPI is horrific.

  • Can mimic any finely-tuned MPI program

    • Shared message  view

    • Send/recv  acquire_view

  • Essential differences

    • View is location transparent

    • More barriers in VOPP

Zhiyi’s RSL


Implementation

Implementation

  • VODCA: View-Oriented, Distributed, Cluster-based Approach to parallel computing

  • VODCA version 1.0

    • Released as an open source software

    • A library run at the user space

    • Based on View-based Consistency

    • Use an efficient consistency protocol VOUPID

Zhiyi’s RSL


View based consistency

View-based Consistency

  • Condition for View-based Consistency

    • Before a processor Pi is allowed to access a view by calling acquire_view or acquire_Rview, all previous write accesses to data objects of the view must be performed with respect to Pi according to their causal order.

  • In VOPP, barriers are only used for synchronization and have nothing to do with consistency maintenance for DSM.

Zhiyi’s RSL


Consistency protocols

Consistency protocols

  • They are page based

  • Update protocol

    • Modify immediately

  • Invalidation protocol

    • Use a write notice to invalidate a page

    • When the page is accessed, a page fault causes the fetch of diffs which are applied on the page

Zhiyi’s RSL


Consistency protocols cont

Consistency protocols (cont.)

  • Home-based protocol

    • Based on invalidate protocol, but

    • For each page, use a copy as its home

    • When a diff is created, it is applied to the home copy immediately

    • When the page is accessed, a page fault causes the fetch of the home copy (Pros: resolve the diff accumulation problem)

Zhiyi’s RSL


The voupid protocol

The VOUPID protocol

  • View-Oriented Update Protocol with Integrated Diff

    • Based on the update protocol

    • Diffs of a page of a view are merged into a single diff

    • The single diff is used to update the page when the view is acquired

Zhiyi’s RSL


Experiment

Experiment

  • Use a cluster computer

    • The cluster computer, in Tsinghua Univ., consists of 128 Itanium 2 running Linux 2.4, connected by InfiniBand. Each node has two 1.3 GHz processors and 4 Gbytes RAM. We run two processes on each node.

  • We used four applications, Integer Sort (IS), Gauss, Successive Over-Relaxation (SOR), and Neural Network (NN).

Zhiyi’s RSL


Related systems

Related systems

  • TreadMarks (TMK) is a state-of-the-art Distributed Shared Memory system based on traditional parallel programming.

  • Message Passing Interface (MPI) is a standard for message passing-based parallel programming. We used LAM/MPI.

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Performance of nn

Performance of NN

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Performance of is

Performance of IS

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Performance of sor

Performance of SOR

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Performance of gauss

Performance of Gauss

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Future work on vopp

Future work on VOPP

  • More benchmarks/applications

  • Performance evaluation on larger clusters

  • Optimized implementation of barriers for VOPP

  • More auxiliary utilities for VOPP programmers

  • A view-based debugger for VOPP

  • A fault-tolerant system for VODCA

Zhiyi’s RSL


Questions

Questions?

Zhiyi’s RSL


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