在C語言中,要實(shí)現(xiàn)多個(gè)線程并發(fā)執(zhí)行并找到最大值,你可以使用POSIX線程庫(pthread)和互斥鎖(mutex)。下面是一個(gè)簡(jiǎn)單的示例:
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <limits.h>
#define NUM_THREADS 10
int max_value = INT_MIN;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
void *find_max(void *arg) {
int thread_id = *(int *)arg;
int local_max = INT_MIN;
// 模擬計(jì)算每個(gè)線程的最大值
for (int i = 0; i < 1000; i++) {
if (local_max < i) {
local_max = i;
}
}
// 使用互斥鎖保護(hù)全局變量max_value
pthread_mutex_lock(&mutex);
if (local_max > max_value) {
max_value = local_max;
}
pthread_mutex_unlock(&mutex);
return NULL;
}
int main() {
pthread_t threads[NUM_THREADS];
int thread_ids[NUM_THREADS];
// 創(chuàng)建線程
for (int i = 0; i < NUM_THREADS; i++) {
thread_ids[i] = i;
pthread_create(&threads[i], NULL, find_max, &thread_ids[i]);
}
// 等待線程結(jié)束
for (int i = 0; i < NUM_THREADS; i++) {
pthread_join(threads[i], NULL);
}
printf("Max value: %d\n", max_value);
return 0;
}
這個(gè)示例中,我們創(chuàng)建了10個(gè)線程,每個(gè)線程都會(huì)計(jì)算一個(gè)局部最大值。然后,我們使用互斥鎖保護(hù)全局變量max_value
,以確保在更新最大值時(shí)不會(huì)發(fā)生競(jìng)爭(zhēng)條件。最后,主線程等待所有子線程結(jié)束后,輸出最大值。