#include <HashedLock.h>

Public Types
typedef LockType	Lock

typedef Poco::SharedPtr < HashedLock< Lock, ID, Hash > >	Ptr

Public Member Functions
	HashedLock ()

	HashedLock (unsigned int count)

void	delayedInit (unsigned int count)

Lock &	find (const ID &id)

Lock &	at (const unsigned int index)

unsigned int	size () const

Protected Member Functions
void	assureInitialized ()

Detailed Description

template<typename LockType, typename ID, typename Hash = typename ID::Hash>
class BeeeOn::HashedLock< LockType, ID, Hash >

HashedLock is useful to reduce overhead of fine-grained locking strategy. If there are too many instances that should be locked during its processing and maintaining a separate lock for each instance would be expensive, this class can help to reduce this cost. The instances are sorted into buckets that share a single lock. The sorting is performed via a hash function. Thus, if the hash function has a low collision rate, the performance of this strategy would be very close to the fine-grained locking.

Common usage with Poco::FastMutex:

#define GOOD_PRIME 31 HashedLock<FastMutex, MyType, MyTypeHash> lock(GOOD_PRIME);

startThread(lock, threadWork); startThread(lock, threadWork); startThread(lock, threadWork);

void threadWork(auto &lock) { MyType &type = obtainOne(); FastMutex::ScopedLock guard(lock.find(type)); ... }

The probability of sharing a lock depends on the number of threads (usually fixed) and the quality of the used hash function.