PVM Parallel Virtual Machine

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PVM(Parallel Virtual Machine)
Course CS683 Computer Architecture Prof.
Moreshwar R Bhujade
By Vishal Prajapati
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Contents

• Introduction
• Features of PVM
• PVM as a System
• Example (Fork Join)
• Summary

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Introduction

• PVM is a software tool for parallel networking of
  computers.
• Major Acceptance because of
• Developements in MPP
• Powerfull computers (Blue gene)
• Widespread use of distributed systems.
• Source code
• netlib (http//en.wikipedia.org/wiki/Netlib)

The Key consept is PVM allows to see the
collection of computers as a one gient high
performance machine.
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Introduction

• PVM is a software tool for parallel networking of
  computers.
• Major Acceptance because of
• Developements in MPP
• Powerfull computers (Blue gene)
• Widespread use of distributed systems.
• Source code
• netlib (http//en.wikipedia.org/wiki/Netlib)

The Key consept is PVM allows to see the
collection of computers as a one gient high
performance machine.
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PVM (Physical Vs Logical View)
Source ftp//ftp.netlib.org
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Featurs of PVM - 1

• Portable
• Runs on nearly every Unix machine plus many
  shared- and distributed-memory multipro-cessors.
• Heterogeneous
• Any types of machines can be combined in a
  single virtual machine
• Scalable
• Virtual machines can include hundreds of host
  computers and run thousands of tasks.
• Dynamic configuration
• computers can be dynamically added and deleted
  from the parallel virtual machine by the
  application or manually.
• Hooks for fault tolerance
• Application can be noticed via messages of lost
  processes processors or addition of new
  resources.

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Featurs of PVM - 2

• Dynamic process groups
• user-defined process grouping for functions like
  broadcast and barrier. Groups can overlap and
  change dynamically during an application.
• Signals
• PVM tasks can send signals to other tasks.
• Multiple message buffers
• Allows easier development of PVM math libraries
  graphical interfaces etc.
• Tracing
• Call-level tracing built into PVM library.
• Can be customized
• User can write manager tasks to implement custom
  scheduling policies.

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PVM - System

• Composed of Two parts
• PVM daemon pvmd3 or pvmd
• For accepting remote connection and connecting
  to remote machines
• PVM library libpvm3.a
• Contains user callable routines for message
  passing spawning processes coordinating tasks
  and modifying the virtual machine.

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PVM Example (Fork Join)
/ Fork Join Example Demonstrates how
to spawn processes and exchange messages / /
defines and prototypes for the PVM library
/ include ltpvm3.hgt / Maximum number of
children this program will spawn / define
MAXNCHILD 20 / Tag to use for the joing
message / define JOINTAG 11 int main(int
argc char argv) / number of tasks to
spawn use 3 as the default / int ntask
3 / return code from pvm calls / int
info
/ my task id / int mytid / my
parents task id / int myparent /
children task id array / int
childMAXNCHILD int i mydata buf len
tag tid / find out my task id number /
mytid pvm_mytid() / check for error
/ if (mytid lt 0) / print out the
error / pvm_perror(argv0) /
exit the program / return -1
/ find my parents task id number /
myparent pvm_parent()
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PVM Example (Fork Join)
/ exit if there is some error other than
PvmNoParent / if ((myparent lt 0)
(myparent ! PvmNoParent))
pvm_perror(argv0) pvm_exit()
return -1 / if i dont have a
parent then i am the parent / if (myparent
PvmNoParent) / find out how many
tasks to spawn / if (argc 2) ntask
atoi(argv1) / make sure ntask is
legal / if ((ntask lt 1) (ntask gt
MAXNCHILD)) pvm_exit() return 0 /
spawn the child tasks / info
pvm_spawn(argv0 (char)0 PvmTaskDefault
(char)0 ntask child) /
print out the task ids / for (i 0 i lt
ntask i) if (childi lt 0) /
print the error code in decimal/
printf( d childi) else /
print the task id in hex /
printf(tx\t childi)
putchar(\n) / make sure spawn
succeeded / if (info 0) pvm_exit()
return -1 / only expect responses
from those spawned correctly / ntask
info
for (i 0 i lt ntask i) / recv
a message from any child process /
buf pvm_recv(-1 JOINTAG) if (buf
lt 0) pvm_perror(calling recv) info
pvm_bufinfo(buf len tag tid)
if (info lt 0) pvm_perror(calling pvm_bufinfo)
info pvm_upkint(mydata 1 1)
if (info lt 0) pvm_perror(calling
pvm_upkint) if (mydata ! tid)
printf(This should not happen!\n)
printf(Length d Tag d Tid tx\n len tag
tid) pvm_exit()
return 0 / im a child / info
pvm_initsend(PvmDataDefault) if (info lt 0)
pvm_perror(calling pvm_initsend)
pvm_exit() return -1 info
pvm_pkint(mytid 1 1) if (info lt 0)
pvm_perror(calling pvm_pkint) pvm_exit()
return -1 info pvm_send(myparent
JOINTAG) if (info lt 0)
pvm_perror(calling pvm_send) pvm_exit()
return -1 pvm_exit() return 0
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PVM Example

• It Contains both parent and child code.
• This function must be called before any other
  call. This call must be positive number.
• This call tells what goes wrong with the last
  call.
• Retuns the Parent ID or else will retrn Error
  code PvmNoParent says that the process is
  spawned by user and not by any other process.

/ find out my task id number / mytid
pvm_mytid()
pvm_perror(argv0)
/ find my parents task id number /
myparent pvm_parent()
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PVM Example

• Following code differenciate the parent of all
  childs.
• So by this you can differenciate the code of top
  process and child code.
• This is the code which spawns childs.

/ if i dont have a parent then i am the
parent / if (myparent PvmNoParent)
/ spawn the child tasks / info
pvm_spawn(argv0 (char)0 PvmTaskDefault
(char)0 ntask child)
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PVM Example
/ spawn the child tasks / info
pvm_spawn(argv0 (char)0 PvmTaskDefault
(char)0 ntask child)

• Perameters
• First perameter gives the name of the program
  that the child should run.
• Second perameter is the arguments that can be
  passed to child
• Third perameter this says that where the
  child should spawn. We can give specific
  architecture or host name where the child can
  spawn
• Fourth perameter will have the values of the
  third perameter
• Fifth perameter specifies the number of the
  childs to be spawned.
• Last perameter is the array name which holds
  the child Ids.
• This Function is returning the no of child
  successfully spawned which should be equal to the
  sent number n the 5th perameter other wise
  something gone wrong.

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PVM Example

• Following code is the waiting blocking call of
  parent.
• So by this parent is waiting for all the childs
  to send the join message.
• Parent gets the data from the child via the
  message and the following code gets the data
  from the buffer.
• After getting the join messages from all the
  childs parent also exits pvm.

/ recv a message from any child process / buf
pvm_recv(-1 JOINTAG)
info pvm_bufinfo(buf len tag tid)
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PVM Example

• Following code is run by child.
• First line - For message to be sent first we need
  to create the buffer to send the data.
• Second line We are adding the childs Id to the
  message.
• Third line sending the join call to the parent
  with the message attached.
• Fourth line calls off the child from pvm and
  distroy its memory references.

info pvm_initsend(PvmDataDefault) info
pvm_pkint(mytid 1 1) info
pvm_send(myparent JOINTAG) pvm_exit()
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PVM Example (Fork Join)
Output forkjoin t10001c t40149 tc0037
Length 4 Tag 11 Tid t40149 Length 4 Tag 11
Tid tc0037 Length 4 Tag 11 Tid t10001c
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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Summary
PVM is a software system that enables a
collection of heterogeneous computers to be used
as a coherent and flexible concurrent
computational resource or a Parallel Virtual
Machine.
Thank You