#pragma omp threadprivate

Purpose

The omp threadprivate directive makes the named file-scope, namespace-scope, or static block-scope variables private to a thread.

Syntax

                                 .-,------------.   
                                 V              |   
>>-#--pragma--omp threadprivate----(identifier)-+--------------><

where identifier is a file-scope, name space-scope or static block-scope variable.

Usage

Each copy of an omp threadprivate data variable is initialized once prior to first use of that copy. If an object is changed before being used to initialize a threadprivate data variable, behavior is unspecified.

A thread must not reference another thread's copy of an omp threadprivate data variable. References will always be to the master thread's copy of the data variable when executing serial and master regions of the program.

Use of the omp threadprivate directive is governed by the following points:

• An omp threadprivate directive must appear at file scope outside of any definition or declaration.
• The omp threadprivate directive is applicable to static-block scope variables and may appear in lexical blocks to reference those block-scope variables. The directive must appear in the scope of the variable and not in a nested scope, and must precede all references to variables in its list.
• A data variable must be declared with file scope prior to inclusion in an omp threadprivate directive list.
• An omp threadprivate directive and its list must lexically precede any reference to a data variable found in that list.
• A data variable specified in an omp threadprivate directive in one translation unit must also be specified as such in all other translation units in which it is declared.
• Data variables specified in an omp threadprivate list must not appear in any clause other than the copyin, copyprivate, if, num_threads, and schedule clauses.
• The address of a data variable in an omp threadprivate list is not an address constant.
• A data variable specified in an omp threadprivate list must not have an incomplete or reference type.