I am using tbb::concurrent_vector nodes_ to add multiple nodes to a tree in parallel. The issue arises when I attempt to return nodes_.size(). A race condition occurs when two threads add a node concurrently, causing nodes_.size() to not return the desired outcome.
While I could use a mutex to address this race condition, it would negate the benefits of adding nodes in parallel, making concurrent_vector unnecessary.
Is there a way to continue using concurrent_vector while avoiding race conditions with size()?
Here’s a simplified version of my code, that is run in parallel by multiple threads
int PTree::makeNode(int item) {
nodes_.push_back(PNode(item));
return nodes_.size() - 1;
}
In tbb:concurrent_vector using size() to find the position of the last element you inserted is wrong, you cannot do both operations atomically, instead use the returned iterator from push_back()
int PTree::makeNode(int item) {
auto it = nodes_.push_back(PNode(item));
return static_cast<int>(std::distance(nodes_.begin(), it));
}