PRIVATE Clause

• 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

Questions:

For the C/C++ and Fortran THREADPRIVATE example codes, what output would you expect for alpha[3] and beta[3]? Why?