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1.2 Current Parallel Programming Paradigms - page 16 / 33

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Chapter 3

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Recovery Modes

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The user has three possibilities how the recovery procedure can be started:

  • 1.

    FTMPI RECOVERY MODE AUTO: as soon as the MPI library re- alizes, that a death event has occured, it automatically starts the re- covery process. No interaction from the application is required. Af- ter the recovery has been successfully finished, the error handler of MPI COMM WORLD is called, since other communicators are not available after recovery. The state of communicators, groups and other objects are defined in later sections.

  • 2.

    FTMPI RECOVERY MODE MANUAL: like on any other error, the MPI library calls the error handler attached to the current commu- nicator. The user is however not allowed to call any MPI function involving communication before the recovery has been started.

To start the recovery, the user has to call MPI Comm dup on MPI- COMM WORLD. The input argument of MPI Comm dup should be MPI COMM WORLD, the output argument is undefined and should be ignored by the application.

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oldcomm = MPI_COMM_WORLD; MPI_Comm_dup ( oldcomm,

newcomm );

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Rationale The semantics chosen to initiate the recovery proce- dure manually has once again been driven by the desire to avoid introducing a new MPI function. Introducing a separate function in later version to avoid the dual functionality of MPI Comm dup is highly recommended.

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