94 lines
2.3 KiB
C
94 lines
2.3 KiB
C
// Description: This program uses semaphores to create a square wave between two threads.
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// The period of the square wave is timed and displayed after the threads have finished.
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#include <stdio.h>
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#include <pthread.h>
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#include <semaphore.h>
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#include <stdlib.h>
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#include <time.h>
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#define DEBUG 0
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#define NUM_PERIODS 100e3
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sem_t high_sem, low_sem;
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struct timespec start_time, end_time;
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// Array to store timestamps of each period
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struct timespec timestamps[NUM_PERIODS];
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void* high() {
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for (int i = 0; i < NUM_PERIODS; i++) {
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sem_wait(&high_sem);
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if (clock_gettime(CLOCK_MONOTONIC, ×tamps[i]) != 0) {
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perror("clock_gettime failed");
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exit(1);
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}
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#if DEBUG
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printf("%d: HIGH\n", i);
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#endif
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sem_post(&low_sem);
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}
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return NULL;
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}
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void* low() {
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for (int i = 0; i < NUM_PERIODS; i++) {
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sem_wait(&low_sem);
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#if DEBUG
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printf("%d: LOW\n", i);
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#endif
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sem_post(&high_sem);
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}
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return NULL;
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}
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int main() {
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pthread_t high_thread, low_thread;
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sem_init(&high_sem, 0, 1); // high_sem starts
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sem_init(&low_sem, 0, 0);
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pthread_create(&high_thread, NULL, high, NULL);
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pthread_create(&low_thread, NULL, low, NULL);
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pthread_join(high_thread, NULL);
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pthread_join(low_thread, NULL);
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sem_destroy(&high_sem);
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sem_destroy(&low_sem);
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int period;
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int min_period;
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int max_period;
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int sum_of_periods = 0;
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// Print periods for each iteration
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for (int i = 1; i < NUM_PERIODS; i++) {
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sum_of_periods += period;
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period = (timestamps[i].tv_sec - timestamps[i - 1].tv_sec) * 1e9 + (timestamps[i].tv_nsec - timestamps[i - 1].tv_nsec);
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if (i == 1) {
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min_period = period;
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max_period = period;
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} else {
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if (period < min_period) {
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min_period = period;
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}
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if (period > max_period) {
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max_period = period;
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}
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}
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//printf("Period %d: %lld nanoseconds\n", i, periods[i]);
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//printf("%lld\n", periods[i]);
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}
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printf("Minimum period: %d nanoseconds\n", min_period);
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printf("Maximum period: %d nanoseconds\n", max_period);
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printf("Average period: %f nanoseconds\n", (float)sum_of_periods / (NUM_PERIODS - 1));
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return 0;
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}
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