Write a multithreaded pi estimator. Create $20$ threads. Have each thread generate $10000($x$,$y$)$ pairs. Use srand$48\_$r to seed the random number generator with the thread's ID $($your $20$ threads should be numbered $0-19,$ with each thread's id value passed in during the call to pthread$\_$create$).$ Use drand$48\_$r to generate random floating$-$point numbers between $0$ and $1.$ Do not strictly follow the website example because your answer will be "wrong"; also srand$()$ and rand$()$ aren't thread$-$safe which is why we cannot rely on them here.

struct drand$48\_$data randbuf;

srand$48\_$r$($threadid$,$ &randbuf$)$;

double randx, randy;

for$($int i $=0$; i $<10000$; i$++)\{$

drand$48\_$r$($&randbuf, &randx$)$;

drand$48\_$r$($&randbuf, &randy$)$;

$//$you can calculate and record circle$/$square points here

$\}$

Use randx and randy to determine whether the $($randx$,$ randy$)$ coordinate is inside of the unit circle or not. All threads should contribute to this count. Make sure you eliminate the race condition by protecting the shared variables with a mutex. Make sure you wait for each of the $20$ threads to complete all of its $10,000$ iterations. Calculate the estimate for pi when all threads are done.

pi $=4*($double$)($circle$\_$points$)/$ square$\_$points;

Finally, print the estimated value with printf$("\%\mathrm{.}7$g

$",...)$ and submit the estimate by pasting