Implementing thread-safe arrays
I want to implement a array-liked data structure allowing multiple threads to modify/insert items simultaneously. How can I obtain it in regard to performance? I implemented a wrapper class around std::vector and I used critical sections for synchronizing threads. Please have a look at my code below. Each time a thread want to work on the internal data, it may have to wait for other threads. Hence, I think its performance is NOT good. :( Is there any idea?
class parallelArray{
private:
std::vector<int> data;
zLock dataLock; // my predefined class for synchronizing
public:
void insert(int val){
dataLock.lock();
data.push_back(val);
dataLock.unlo开发者_StackOverflow中文版ck();
}
void modify(unsigned int index, int newVal){
dataLock.lock();
data[index]=newVal; // assuming that the index is valid
dataLock.unlock();
}
};
Take a look at shared_mutex in the Boost library. This allows you to have multiple readers, but only one writer
http://www.boost.org/doc/libs/1_47_0/doc/html/thread/synchronization.html#thread.synchronization.mutex_types.shared_mutex
The best way is to use some fast reader-writer lock. You perform shared locking for read-only access and exclusive locking for writable access - this way read-only access is performed simultaneously.
In user-mode Win32 API there are Slim Reader/Writer (SRW) Locks available in Vista and later.
Before Vista you have to implement reader-writer lock functionality yourself that is pretty simple task. You can do it with one critical section, one event and one enum/int value. Though good implementation would require more effort - I would use hand-crafted linked list of local (stack allocated) structures to implement fair waiting queue.
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