Work-Sharing Constructs
SINGLE Directive

• The SINGLE directive specifies that the enclosed code is to be executed by only one thread in the team.

• May be useful when dealing with sections of code that are not thread safe (such as I/O)

Format:

Fortran	!$OMP SINGLE [clause ...] PRIVATE (list) FIRSTPRIVATE (list) block !$OMP END SINGLE [ NOWAIT ]
C/C++	#pragma omp single [clause ...] newline private (list) firstprivate (list) nowait structured_block

Clauses:

• Threads in the team that do not execute the SINGLE directive, wait at the end of the enclosed code block, unless a NOWAIT/nowait clause is specified.

• Clauses are described in detail later, in the Data Scope Attribute Clauses section.

Restrictions:

• It is illegal to branch into or out of a SINGLE block.