ele709 lab 3.2, C (gcc)

Language: Layout:

#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <pthread.h>

struct thread_info {
double a, b; // The numbers a and b
char op; // The math iteration to be performed: +,-,*,/
int maxitr; // The number of iterations to be performed
double c; // The result: c = a <op> b
double exec_time; // The execution time per iteration in nsec
};

typedef struct thread_info thread_info_t;

void *func(void *arg)
{
   struct timespec time_1, time_2;
   double exec_time;
   thread_info_t *info;
   int i, maxitr;
   volatile double a, b, c, count;
   // char op; part of a convoluted plan I had. Ignore for the moment. Remove in final copy.

info = (thread_info_t *)arg;
   maxitr = info->maxitr;

b = 2.3; 
   a = 4.5;

exec_time = 0.0;

clock_gettime(CLOCK_REALTIME, &time_1);
    
   if (count == 0){
       for (i = 0; i < maxitr; i++) {
             c = a + b;
       } 
       count = 1;
   }
   else if (count == 1) {
       for (i = 0; i < maxitr; i++) {
             c = a - b;
       }
       count = 2;
   }
   else if (count == 2) {
       for (i = 0; i < maxitr; i++) {
             c = a * b;
       }
       count = 3;
   }
   else if (count == 3){	    
       for (i = 0; i < maxitr; i++) {
             c = a / b;
       }
       count = 0;
   }
   else{
   		printf("A failure, your efforts notwithstanding.\n");
       count = 0;
	}
    
   
   printf("Computation: %lf\n", c);
   clock_gettime(CLOCK_REALTIME, &time_2);

exec_time = (time_2.tv_sec - time_1.tv_sec);
   exec_time = exec_time + (time_2.tv_nsec - time_1.tv_nsec)/1.0e9;

info->exec_time = exec_time;

pthread_exit(NULL);
   
}

int main(void)
{
   pthread_t thread1;
   thread_info_t info1;
   double maxitr;

maxitr = 5.0e8;

info1.maxitr = (int)maxitr;
   
    /*
   printf("Welcome to the Experiment.\n");
   
   printf("Please enter the equation: \n");
   scanf("%lf %c %lf",&a, &op, &b);
   
   This might be more useful later? Or I am pointlessly increasing the complexity of this assignment. 
   
   Pass the input to the structure via pointers
   
   alternatively, set up a loop that generates four pthreads - one per operation. 
   Have them run sequentially, by putting the pthread_join before the loop cycles. 
   Pass the loop counter to the function which using a if else nest sets the op to be performed 1 -> + etc. 
   
   */
   for (int t=0; t<4; t++){
   if (pthread_create(&thread1, NULL, &func, &info1) != 0) {
           printf("Error in creating thread 1\n");
           exit(1);
   }

pthread_join(thread1, NULL);
   printf("Exec time for thread1 = %lf sec\n", info1.exec_time);
   }
    
   pthread_exit(NULL);
   //main(); pointlessly trying to cycle. 
}

Show compiler warnings [ + ] Compiler args [ + ] Show input
Compilation time: 0.13 sec, absolute running time: 4.06 sec, cpu time: 5.3 sec, memory peak: 3 Mb, absolute service time: 4,2 sec