OpenMP Directives: Data Scope Attribute Clauses: PRIVATE Clause
Purpose:
The PRIVATE clause declares variables in its list to be private to each thread.
Format:
Fortran
PRIVATE (list)
C/C++
private (list)
Notes:
- PRIVATE variables behave as follows:
- A new object of the same type is declared once for each thread in the team
- All references to the original object are replaced with references to the new object
- Variables declared PRIVATE should be assumed to be uninitialized for each thread
- Comparison between PRIVATE and THREADPRIVATE:
| PRIVATE | THREADPRIVATE | |
|---|---|---|
| Data Item | C/C++: variable Fortran: variable or common block |
C/C++: variable Fortran: common block |
| Where Declared | At start of region or work-sharing group | In declarations of each routine using block or global file scope |
| Persistent? | No | Yes |
| Extent | Lexical only - unless passed as an argument to subroutine | Dynamic |
| Initialized | Use FIRSTPRIVATE | Use COPYIN |
