test

吕锦中202441429012406/psum64.c

@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <sys/time.h>
+
+#define MAX_THREADS 64
+#define N 1000000000LL
+
+long long global_sum = 0;
+long long nelems_per_thread;
+pthread_mutex_t mutex;
+
+void *sum_thread(void *arg) {
+    long long start = *(long long *)arg;
+    long long local_sum = 0;
+    long long end = start + nelems_per_thread;
+    if (end > N) end = N;
+    for (long long i = start; i < end; i++) {
+        local_sum += i;
+    }
+    pthread_mutex_lock(&mutex);
+    global_sum += local_sum;
+    pthread_mutex_unlock(&mutex);
+    return NULL;
+}
+
+double get_time() {
+    struct timeval tv;
+    gettimeofday(&tv, NULL);
+    return tv.tv_sec + tv.tv_usec / 1000000.0;
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s <num_threads>\n", argv[0]);
+        return 1;
+    }
+
+    int nthreads = atoi(argv[1]);
+    if (nthreads > MAX_THREADS) nthreads = MAX_THREADS;
+
+    nelems_per_thread = N / nthreads;
+    pthread_mutex_init(&mutex, NULL);
+
+    pthread_t threads[MAX_THREADS];
+    long long starts[MAX_THREADS];
+
+    double t_start = get_time();
+
+    for (int i = 0; i < nthreads; i++) {
+        starts[i] = i * nelems_per_thread;
+        pthread_create(&threads[i], NULL, sum_thread, &starts[i]);
+    }
+
+    for (int i = 0; i < nthreads; i++) {
+        pthread_join(threads[i], NULL);
+    }
+
+    double t_end = get_time();
+    double elapsed = t_end - t_start;
+
+    printf("Threads: %d, Sum: %lld, Time: %.6f s\n", nthreads, global_sum, elapsed);
+
+    pthread_mutex_destroy(&mutex);
+    return 0;
+}