多线程处理

include

include

define NUM_THREADS 5

int sum = 0;
pthread_mutex_t sum_mutex;

static void *say_hello(void *args)
{
cout << “hello in thread ” << ((int )args) << endl;
pthread_mutex_lock(&sum_mutex);
cout << “before sum is ” << sum << ” in thread ” << ((int)args) << endl;
sum += ((int)args);
cout << “after sum is ” << sum << ” in thread ” << ((int)args) << endl;
pthread_mutex_unlock(&sum_mutex);

// int status = 10 + ((int )args);
pthread_exit(0);
}

int main()
{
pthread_t tids[NUM_THREADS];
cout << “hello in main .. “<< endl;
int indexes[NUM_THREADS];

pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

pthread_mutex_init(&sum_mutex, NULL);

for(int i = 0; i < NUM_THREADS; ++i) {
indexes[i] = i;
int ret = pthread_create(&tids[i], &attr, say_hello, (void*)&(indexes[i]));

//cout << "Current pthread id = " << tids[i] << endl;if(ret != 0) {  cout << "pthread_create error: error_code = " << ret << endl;}

}
pthread_attr_destroy(&attr);
void *status;
for(int i = 0; i < NUM_THREADS; ++i) {

int ret = pthread_join(tids[i], &status);
if (ret != 0) {
cout << “pthread_join error:error_code=” << ret << endl;
} else {
//cout << “pthread_join get status:” << (long)status << endl;
}
cout << “finally sum is ” << sum << endl;
pthread_mutex_destroy(&sum_mutex);

}
// pthread_exit(NULL);
}

编译方式：
g++ -o muti_thread_test_1 muti_thread_test_1.cpp -lpthread

./muti_thread_test_1

结果：

hello in main ..
hello in thread hello in thread 01

hello in thread 2before sum is 0
in thread 0
hello in thread 3
hello in thread 4after sum is 0 in thread 0

before sum is 0 in thread 4
after sum is 4 in thread 4
before sum is 4 in thread 2
after sum is 6 in thread 2
before sum is 6 in thread 3
after sum is 9 in thread 3
before sum is 9 in thread 1
after sum is 10 in thread 1
finally sum is 10
finally sum is 10
finally sum is 10
finally sum is 10
finally sum is 10

again：

hello in main ..
hello in thread hello in thread 01
hello in thread 2
before sum is 0 in thread 2

after sum is 2 in thread 2
hello in thread 4
before sum is hello in thread 23 in thread
0
after sum is 2 in thread 0
before sum is 2 in thread 1
after sum is 3 in thread 1
before sum is 3 in thread 4
after sum is 7 in thread 4
before sum is 7 in thread 3
after sum is 10 in thread 3
finally sum is 10
finally sum is 10
finally sum is 10
finally sum is 10
finally sum is 10