What does it mean? That means that each iterator you obtain from a ConcurrentHashMap is designed to be used by a single thread and should not be passed around. This includes the syntactic sugar that the for-each loop provides. What happens if I try to iterate the map with two threads at the same time? … Read more
If a method (instance or static) only references variables scoped within that method then it is thread safe because each thread has its own stack: In this instance, multiple threads could call ThreadSafeMethod concurrently without issue. public class Thing { public int ThreadSafeMethod(string parameter1) { int number; // each thread will have its own variable … Read more
This would be simpler: return Interlocked.Increment(ref COUNTER); MSDN Interlocked.Increment
Your implementation is correct. The .NET Framework does not provide a built-in concurrent hashset type, unfortunately. However, there are some workarounds. ConcurrentDictionary (recommended) This first one is to use the class ConcurrentDictionary<TKey, TValue> in the namespace System.Collections.Concurrent. In the case, the value is pointless, so we can use a simple byte (1 byte in memory). … Read more
Lee’s approach can be simplified further public static void InvokeIfRequired(this Control control, MethodInvoker action) { // See Update 2 for edits Mike de Klerk suggests to insert here. if (control.InvokeRequired) { control.Invoke(action); } else { action(); } } And can be called like this richEditControl1.InvokeIfRequired(() => { // Do anything you want with the control … Read more
If you declare the method as synchronized (as you’re doing by typing public synchronized void addA()) you synchronize on the whole object, so two thread accessing a different variable from this same object would block each other anyway. If you want to synchronize only on one variable at a time, so two threads won’t block … Read more
The relevant section 6.7: such a variable is initialized the first time control passes through its declaration; such a variable is considered initialized upon the completion of its initialization. […] If control enters the declaration concurrently while the variable is being initialized, the concurrent execution shall wait for completion of the initialization. Then there’s a … Read more
Queue.Queue and collections.deque serve different purposes. Queue.Queue is intended for allowing different threads to communicate using queued messages/data, whereas collections.deque is simply intended as a datastructure. That’s why Queue.Queue has methods like put_nowait(), get_nowait(), and join(), whereas collections.deque doesn’t. Queue.Queue isn’t intended to be used as a collection, which is why it lacks the likes … Read more
1. How is safely defined? Semantically. In this case, this is not a hard-defined term. It just mean “You can do that, without risk”. 2. If a program can be safely executed concurrently, does it always mean that it is reentrant? No. For example, let’s have a C++ function that takes both a lock, and … Read more
Great questions, I think the documentation could do with some more detail. io() is backed by an unbounded thread-pool and is the sort of thing you’d use for non-computationally intensive tasks, that is stuff that doesn’t put much load on the CPU. So yep interaction with the file system, interaction with databases or services on … Read more