c++ - 多线程二叉树算法

Question

因此，我尝试了一种方法来锁定每个节点，但这需要大量的锁定和解锁……这当然需要相当多的开销。我想知道是否有人知道更有效的算法。这是我的第一次尝试:

typedef struct _treenode{
   struct _treenode *leftNode;
   struct _treenode *rightNode;
   int32_t data;
   pthread_mutex_t mutex;
}TreeNode;

pthread_mutex_t _initMutex = PTHREAD_MUTEX_INITIALIZER;

int32_t insertNode(TreeNode **_trunk, int32_t data){
   TreeNode **current;
   pthread_mutex_t *parentMutex = NULL, *currentMutex = &_initMutex;

   if(_trunk != NULL){
      current = _trunk;
      while(*current != NULL){
         pthread_mutex_lock(&(*current)->mutex);
         currentMutex = &(*current)->mutex;
         if((*current)->data < data){
            if(parentMutex != NULL)
               pthread_mutex_unlock(parentMutex);
            pthreadMutex = currentMutex;
            current = &(*current)->rightNode;
         }else if((*current)->data > data){
            if(parentMutex != NULL)
               pthread_mutex_unlock(parentMutex);
            parentMutex = currentMutex;
            current = &(*current)->leftNode;
         }else{
            pthread_mutex_unlock(currentMutex);
            if(parentMutex != NULL)
               pthread_mutex_unlock(parentMutex);
            return 0;
         }
      }
      *current = malloc(sizeof(TreeNode));
      pthread_mutex_init(&(*current)->mutex, NULL);
      pthread_mutex_lock(&(*current)->mutex);
      (*current)->leftNode = NULL;
      (*current)->rightNode = NULL;
      (*current)->data = data;
      pthread_mutex_unlock(&(*current)->mutex);
      pthread_mutex_unlock(currentMutex);
   }else{
      return 1;
   }
   return 0;
}

int main(){
   int i;
   TreeNode *trunk = NULL;
   for(i=0; i<1000000; i++){
      insertNode(&trunk, rand() % 50000);
   }
}

Answer 1

您不需要锁定您访问的每个节点。你可以这样做。当您要进行插入时锁定节点。做你的插入和解锁。如果另一个线程碰巧需要在它的同一点插入并且节点被锁定，它应该在进一步向下遍历之前等待。一旦节点解锁，它就可以继续遍历树的更新部分。