Program $1$

Given the following program called critSec.c that has a critical section where a shared counter is updated

#include

#include

#define NUM$\_$THREADS $10$

#define ITERATIONS $1000000$

int counter $=0$; $//$ Shared counter

void$*$ increment$($void$*$ arg$)\{$

for $($int i $=0$; i $<$ ITERATIONS; i$++)\{$

$//$ Critical section: increment the shared counter

counter$++$;

$\}$

return NULL;

$\}$

int main$()\{$

pthread$\_$t threads$[$NUM$\_$THREADS$]$;

$//$ Create threads

for $($int i $=0$; i $<$ NUM$\_$THREADS; i$++)\{$

pthread$\_$create$($&threads$[$i$],$ NULL, increment, NULL$)$;

$\}$

$//$ Wait for all threads to finish

for $($int i $=0$; i $<$ NUM$\_$THREADS; i$++)\{$

pthread$\_$join$($threads$[$i$],$ NULL$)$;

$\}$

printf$("$Final counter value: $\%$d

$",$ counter$)$;

return $0$;

$\}$

Start by compiling and running this program. The correct value for the Final Counter should be $10,000,000(1,000,000$ iterations done by $10$ threads.$)$ You will find that the output for Final Counter value will vary a fair bit. This is due to timing errors and a race condition.

Next copy the program to one called critSecMutex.c where you will add a mutex to protect the critical section.

Finally, make another copy of the critSec.c and cally it critSecSemaphore.c$,$ where you add a semaphore to protect the critical section.

Program $2$

Start with the following c$++$ program that has the same race condition as about:

#include

#include

#include

using namespace std;

const int ITERATIONS $=1000000$;

int counter $=0$; $//$ Shared resource

void increment$()\{$

for $($int i $=0$; i $<$ ITERATIONS; i$++)\{$

$//$ Critical section: incrementing the counter

counter$++$;

$\}$

$\}$

int main$()\{$

vector threads;

$//$ Create multiple threads

for $($int i $=0$; i $<10$; i$++)\{$

threads.push$\_$back$($thread$($increment$))$;

$\}$

$//$ Wait for all threads to finish

for $($auto& th : threads$)\{$

th$.$join$()$;

$\}$

cout $<<$ "Final counter value: $"<<$ counter $<<$ endl;

return $0$;

$\}$

Save this as critSec.cpp$.$ Do the same as before and compile and run this to verify that the final count does in fact give different results.

Then create a copy called critSecMonitor.cpp and protect the critical section with a Monitor class.