C Programing Multiple Threads using pthread.h [closed] - c

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I'm trying to learning C Programing and multiple threads. I started programing some basic stuff [like the following], but I got stuck. Can someone give me a hand?
program.c
#include <string.h>
#include <stdio.h>
#include <pthread.h>
#define NUM_THREADS 4
void *main_thread(void *threadID) {
long tid;
tid = (long)threadID;
printf("main thread #%ld!\n", tid);
pthread_exit(NULL);
}
void *first_thread(void *threadID) {
long tid;
tid = (long)threadID;
printf("first thread #%ld!\n", tid);
pthread_exit(NULL);
}
void *second_thread(void *threadID) {
long tid;
tid = (long)threadID;
printf("second thread #%ld!\n", tid);
pthread_exit(NULL);
}
void *last_thread(void *threadID) {
long tid;
tid = (long)threadID;
printf("last thread #%ld!\n", tid);
pthread_exit(NULL);
}
int main () {
pthread_t threads[NUM_THREADS];
int rc;
long t;
for (t=0; t < NUM_THREADS; t++) {
printf("In main Function creating thread %ld\n", t);
rc = pthread_create(&threads[t], NULL, first_thread, (void *)t);
if (rc) {
printf("ERROR; Return code from pthread_create is %d\n", rc);
exit(-1);
}
}
pthread_exit(NULL);
return 0;
}
I will keep updating the codes above as i figure new things out
*Hey guys. i did not compile it properly but now i figured out.
gcc -pthread -o main main.c

Answer 1

This code will calculate the value of e^x by calculating terms of its series ,
in each term we need to calculate power of a number(in this program it is x) and factorial of each corresponding power.
since these two calculations are independent so we make two threads for these two functions that will be run parallel.
after calculating values of these two function (end of these two threads) we need to merge the results (i mean power/factorial) and then we add all these results in another parallel thread which will run after these two threads.
#include<stdio.h>
#include<math.h>
#include<pthread.h>
#include<stdlib.h>
long double x,fact[150],pwr[150],s[1];
int i,term;
void *Power(void *temp)
{
int k;
for(k=0;k<150;k++)
{
pwr[k] = pow(x,k);
//printf("%.2Lf\n",pwr[k]);
}
return pwr;
}
void *Fact(void *temp)
{
long double f;
int j;
fact[0] = 1.0;
for(term=1;term<150;term++)
{
f = 1.0;
for(j=term;j>0;j--)
f = f * j;
fact[term] = f;
//printf("%.2Lf\n",fact[term]);
}
return fact;
}
void *Exp(void *temp)
{
int t;
s[0] = 0;
for(t=0;t<150;t++)
s[0] = s[0] + (pwr[t] / fact[t]);
return s;
}
int main(void)
{
pthread_t thread1,thread2,thread3;
printf("Enter the value of x (between 0 to 100) (for calculating exp(x)) : ");
scanf("%Lf",&x);
printf("\nThreads creating.....\n");
pthread_create(&thread1,NULL,Power,NULL); //calling power function
pthread_create(&thread2,NULL,Fact,NULL); //calling factorial function
printf("Threads created\n");
pthread_join(thread1,NULL);
pthread_join(thread2,NULL);
printf("Master thread and terminated threads are joining\n");
printf("Result collected in Master thread\n");
pthread_create(&thread3,NULL,Exp,NULL);
pthread_join(thread3,NULL);
printf("\nValue of exp(%.2Lf) is : %Lf\n\n",x,s[0]);
exit(1);
}