SEM分析可以将无法直接测量的属性纳入分析。比方说消费者忠诚度。这样就可以将数据分析的范围加大,尤其适合一些比较抽象的归纳性的属性。
struct rwlock
{
sem_t read
sem_t write
int reads
}
void RWLock_Init(rwlock &lock)
{
sem_init(lock.read, 0, 1)
sem_init(lock.write, 0, 1)
lock.reads = 0
}
void Acquir_read_lock(rwlock &lock)
{
sem_wait(&lock.read)
++lock.reads
if(lock.reads == 1)
{
sem_wait(&lock.write)
}
sem_post(&lock.write)
}
void acquir_read_unlock(rwlock &lock)
{
sem_wait(&lock.read)
--lock.reads
if(lock.reads == 0)
{
sem_post(&lock.write)
}
sem_post(&lcok.read)
}
void acquir_write_lock(rwlock &lock)
{
sem_wait(&lock.write)
}
void acquir_write_unlock(rwlock * lock)
{
sem_post(&lock.write)
}
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