PVM: Parallel Virtual Machine A Users' Guide and Tutorial for Networked Parallel Computing

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• PVM Parallel Virtual Machine A Users' Guide and
  Tutorial for Networked Parallel Computing
• Program Examples
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Contents
Program Examples Fork-Join  Fork Join Example
Dot Product  Example program PSDOT.F Failure 
Example program failure.c Matrix Multiply 
Example program mmult.c One-Dimensional Heat
Equation  Example program heat.c Example
program heatslv.c Different Styles of
Communication  
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Overview

• The first example
• forkjoin.c
• Show how to spawn off processes and synchronize
  with them
• The second example
• A Fortran dot product program
• PSDOT.F
• The third example
• failure.c
• Use the pvm_notify() call to create fault
  tolerant applications

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Fork-Join

• To spawn PVM tasks and synchronize with them
• The program spawns several tasks
• Three by default
• Three steps
• The children then synchronize by sending a
  message to their parent task
• The parent receives a message from each of the
  spawned tasks
• Print out information about the message from the
  child tasks

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Fork-Join

• The fork-join program contains the code for both
  the parent and the child tasks
• See the source code of the Fork-Join example

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Fork-Join

• The output of running forkjoin

forkjoin t10001c t40149 tc0037 Length 4, Tag
11, Tid t40149 Length 4, Tag 11, Tid tc0037
Length 4, Tag 11, Tid t10001 c forkjoin 4
t10001e t10001d t4014b tc0038 Length 4, Tag 11,
Tid t4014b Length 4, Tag 11, Tid tc0038 Length
4, Tag 11, Tid t10001d Length 4, Tag 11, Tid
t10001e
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Failure

• The failure example demonstrates
• how one can kill tasks
• How one can find out when tasks exit or fail
• Fining out when a task fails
• Call pvm_notify() after spawning the tasks
• The pvm_notify() call can tells PVM to send the
  calling task a message when certain tasks exit

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Failure

• The task calling pvm_notify() will receive the
  notification, not the tasks given in the task id
  array
• The notify call can also be used to a task when a
  new host has been added or deleted from the
  virtual machine

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Failure

• After requesting notification, the parent task
  then kills one of the children
• After killing one of the spawned tasks, the
  parent waits on a pvm_recv(-1, TASKDIED) for the
  message notifying it the task has died
• The process unpacks the dead tasks id and prints
  it out

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Failure

• See the source code of the Failure example

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Different Styles of Communication

• These example demonstrate various ways of writing
  PVM programs
• In some cases messages are used for
  synchronization
• In others the master processes simply kill of the
  workers when they are no longer needed

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Quiz

• 1210000
• Distribute the above calculation to several PVM
  tasks, for example n tasks
• Kill the middle task, i.e. n/2
• Try to obtain the correct calculating result from
  the remaining n-1 tasks

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Reference

• A Beginners Guide to PVM Virtual Machine,
  available through http//www.itec.uni-klu.ac.at/h
  arald/PVM/pvm_guide.html