Frequent question: Is STL map thread safe?

It isn’t thread safe, insert from two threads and you can end up in an inconstant state.

Is STL vector thread safe?

Well, vector’s interface isn’t optimal for concurrent use. It is fine if the client has access to a lock, but for for the interface to abstract locking for each operation — no. In fact, vector’s interface cannot guarantee thread safety without an external lock (assuming you need operations which also mutate).

Is map insert thread safe?

2 Answers. No, std::map::insert is not thread-safe. There are many reasons why your example may not crash. Your threads may be running in a serial fashion due to the system scheduler, or because they finish very quickly (1000 iterations isn’t that much).

Is std :: map find thread safe?

4 Answers. No, the C++ spec makes no guarantees on thread safety in the spec for operations on any STL containers.

Is tree map thread safe?

TreeMap and TreeSet are not thread-safe collections, so care must be taken to ensure when used in multi-threaded programs. Both TreeMap and TreeSet are safe when read, even concurrently, by multiple threads.

Is vector C++ thread-safe?

Therefore all classes available from the standard, e.g. std::vector, can safely be accessed from multiple threads in the same manner.

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Is ArrayList thread-safe?

Vectors are synchronized. Any method that touches the Vector ‘s contents is thread safe. ArrayList , on the other hand, is unsynchronized, making them, therefore, not thread safe. … So if you don’t need a thread-safe collection, use the ArrayList .

Is std :: map Atomic?

std::atomic as a value of std::map

std::atomic is a C++11 feature, you probably should not expect these things to work very well unless you are willing to use a compiler offering robust support for C++11.

How do you make a map thread safe in C++?

6 Answers. You can use a shared_mutex beside your map to acquire shared or unique access. Generally, a write operation will require unique access, while read operations will require shared access. Any number of threads can acquire shared access, as long as no threads are holding unique access.

What is shared mutex?

The shared_mutex class is a synchronization primitive that can be used to protect shared data from being simultaneously accessed by multiple threads. … shared – several threads can share ownership of the same mutex.

Is std :: Unordered_map thread safe?

No, the standard containers are not thread safe.

Is TreeSet thread-safe?

Although TreeSet isn’t thread-safe, it can be synchronized externally using the Collections.

Is ConcurrentHashMap ordered?

Iteration Order of Mappings

ConcurrentHashMap and HashTable do not preserve the insertion order of mappings in the map. … SynchronizedMap() is backed by the specified map and retains the insertion order of the map.

Is HashSet thread-safe?

HashSet is not thread-safe. You can get thread-safe HashSet using Collections. synchronizedSet method at the cost of performance. … HashSet uses HashMap for storing elements, so the objects should provide good implementation of hashCode() and equals() method to avoid unwanted results.

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