#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define NUM_THREADS 4
#define ARRAY_SIZE 1000000
pthread_mutex_t mutexsum;
float array_one[ARRAY_SIZE]
float array_two[ARRAY_SIZE]
float multiply_total[ARRAY_SIZE];
// Return a random number between 1-9
float getRandomNumber()
{
return ((float)rand() % 10) / ((float)RAND_MAX % 10);
}
// Set the two arrays to random numbers
void init_arrays()
{
int i;
printf("Initializing arrays.\n")
pthread_mutex_init(&mutexsum, NULL);
for ( i = 0; i < ARRAY_SIZE; i++) {
array_one[i] = getRandomNumber();
array_two[i] = getRandomNumber();
}
for ( i = 0; i < ARRAY_SIZE; i++ ) {
multiply_total[i] = 0;
}
}
// multiply arrays together
void *multiply_arrays(void *myID)
{
int i;
float local_multiply_total[ARRAY_SIZE / NUM_THREADS];
int startPos = ((int) myID) * (ARRAY_SIZE / NUM_THREADS);
int endPos = startPos + (ARRAY_SIZE / NUM_THREADS);
printf("myID = %d startPos = %d endPos = %d \n", (int) myID, startPos, endPos);
// initialize local total array
for ( i = 0; i < ARRAY_SIZE / NUM_THREADS; i++ ) {
local_multiply_total[i] = 0;
}
// count up our section of the global arrays
for ( i = startPos; i < endPos; i++) {
local_multiply_total[i] = array_one[i] * array_two[i];
}
// multiply up the partial counts into the global arrays
pthread_mutex_lock (&mutexsum);
for ( i = startPos; i < endPos; i++ ) {
multiply_total[i] = local_multiply_total[i];
}
// release the locks
pthread_mutex_unlock (&mutexsum);
pthread_exit(NULL);
}
// Print multiplied array
void print_results()
{
int i;
int total = 0;
// print out the multiplied array
for ( i = 0; i < ARRAY_SIZE; i++ ) {
//total += char_counts[i];
printf("%f - ", multiply_total[i]);
}
}
main() {
// Declare variables and array of threads
int i;
int rc;
pthread_t threads[NUM_THREADS];
pthread_attr_t attr;
void *status;
srand(time(0));
// Initialize and set thread attribute
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
init_arrays();
// Create threads and give them work
for (i = 0; i < NUM_THREADS; i++ ) {
rc = pthread_create(&threads[i], &attr, multiply_arrays, (void *)i);
if (rc) {
printf("ERROR; return code from pthread_create() is %d\n", rc);
exit(-1);
}
}
// Free attribute and join threads once they complete their work
pthread_attr_destroy(&attr);
for(i=0; i<NUM_THREADS; i++) {
rc = pthread_join(threads[i], &status);
if (rc) {
printf("ERROR; return code from pthread_join() is %d\n", rc);
exit(-1);
}
}
// Print multiplied arrays
print_results();
// Destroy locks and exit pthread
pthread_mutex_destroy(&mutexsum);
printf("Main: program completed. Exiting.\n");
pthread_exit(NULL);
}
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