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threadprivate

Specifies that a variable is private to a thread.

#pragma omp threadprivate(var)

where,

var

A comma-separated list of variables that you want to make private to a thread. var must be either a global- or namespace-scoped variable or a local static variable.

The threadprivate directive supports no OpenMP clauses.

For more information, see 2.7.1 threadprivate Directive.

The threadprivate directive is based on the thread __declspec attribute; limits on __declspec(thread) apply to threadprivate.

You cannot use threadprivate in any DLL that will be loaded via LoadLibrary. This includes DLLs that are loaded with /DELAYLOAD (Delay Load Import), which also uses LoadLibrary.

You can use threadprivate in a DLL that is statically loaded at process startup.

Because threadprivate is based on __declspec(thread), a threadprivate variable will exist in any thread started in the process, not just those threads that are part of a thread team spawned by a parallel region. This is an implementation detail that you may want to be aware of, since you may notice, for example, constructors for a threadprivate user-defined type called more often then expected.

A threadprivate variable of a destructable type is not guaranteed to have its destructor called. For example:

struct MyType 
{
    ~MyType();
};

MyType threaded_var;
#pragma omp threadprivate(threaded_var)
int main() 
{
    #pragma omp parallel
    {}
}

Users have no control as to when the threads constituting the parallel region will terminate. If those threads exist when the process exits, the threads will not be notified about the process exit, and the destructor will not be called for threaded_var on any thread except the one that exits (here, the primary thread). So code should not count on proper destruction of threadprivate variables.

For a sample of using threadprivate, see private.

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