Parallel Computing Lab $$ Assignment $-2($marks $=10)$

$1.$ Modify the program that just prints a line of output from each process $($mpi

output.c$)$ so that the output is printed in process rank order: process $0$s

output first, then process $1$s$,$ and so on$.$

a$.$ Use point$-$to$-$point communication.

b$.$ Use collective communication such as gather.

Copy the source code in your answers file. Launch the Command line and

take a Screenshot of the window with the result of the program

execution including your name. $($copy the Screenshot in your answers

file$).$ Also, provide an explanation showing how the code works.

$[3$ marks$]$

$2.$ What is deadlock in MPI? Explain one scenario showing a Source of

Deadlocks in MPI send and receive functions with sample code?

$[1$ mark$]$

$3.$ Ring Problem

Write a C program that implements a ring algorithm using MPI. The

program calculates the sum of all the process$$s ranks.

The program steps are as follows:

$1.$ All processes initialize MPI.

$2.$ Each process gets its rank and the total number of processes.

$3.$ Each process calculates its left and right neighbours. $($For example, for

processor $3$ its left is equal to $2$ and its right is equal to $4).$

$4.$ Each process initially sends its rank to its right neighbour and receives the

rank of its left neighbour and initialize the sum variable to its rank.

$5.$ Then, repeatedly do the following:

$/*$ File: mpi$\_$output.c

$*$ Purpose: A program in which multiple MPI processes try to print a message.

$*$ Section $3\mathrm{.}3\mathrm{.}1($pp$.97-99.)$

$*/$

#include

#include

int main$($void$)\{$

int my$\_$rank, comm$\_$sz;

MPI$\_$Init$($NULL$,$ NULL$)$;

MPI$\_$Comm$\_$size$($MPI$\_$COMM$\_$WORLD, &comm$\_$sz$)$;

MPI$\_$Comm$\_$rank$($MPI$\_$COMM$\_$WORLD, &my$\_$rank$)$;

printf$("$Proc $\%$d of $\%$d $>$ Does anyone have a toothpick?

$",$ my$\_$rank, comm$\_$sz$)$;

MPI$\_$Finalize$()$;

return $0$;

$\}/*$ main $*/$

a$.$ Each process adds the received value from its left neighbour to its

sum variable.

b$.$ Send the received value from the left neighbour to its right

neighbour.

c$.$ Receive a value from its left neighbour.

$6.$ Steps in point $5$ are repeated until each process receives its own rank.

$7.$ Each process prints its rank and sum to the console.

$8.$ All processes finalize MPI.

Copy the source code in your answers file. Launch the Command line and

take a Screenshot of the window with the result of the program execution

including your name. $($copy the Screenshot in your answers file$).$ Also, provide

an explanation showing how the code works. $[3$ marks$]$

$4.$ Ping$-$Pong Problem

Write a MPI program to implement a ping$-$pong between two processes.

The number of ping$-$pong is given by the user. The program steps are as

follows:

$1.$ Initialize MPI.

$2.$ Get the rank and size of the communicator.

$3.$ Check if the number of processes is equal to $2.$

$4.$ Get the number of ping$-$pong exchanges from the user.

$5.$ Start the ping$-$pong communication loop $($Initially ping$-$pong count $=0)$ :

$$ If the rank is $0,$ send the ping$-$pong count to rank $1$ and receive the

ping$-$pong count from rank $1.$

$$ If the rank is $1,$ receive the ping$-$pong count from rank $0$ and send the

ping$-$pong count to rank $0.$

$$ Increment the ping$-$pong count.

$6.$ Repeat step $5$ until the ping$-$pong count is equal to the number of pingpong exchanges.

$7.$ Finalize MPI.

Copy the source code in your answers file. Launch the Command line and

take a Screenshot of the window with the result of the program execution

including your name. $($copy the Screenshot in your answers file$).$ Also, provide

an explanation showing how the code works. $[3$ marks$]$