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