layout	title	release_number	author	tutorial
tutorial_page	OpenMP Directives: Synchronization Constructs: ORDERED Directive	UCRL-MI-133316	Blaise Barney, Lawrence Livermore National Laboratory	OpenMP

Purpose:

The ORDERED directive specifies that iterations of the enclosed loop will be executed in the same order as if they were executed on a serial processor.
Threads will need to wait before executing their chunk of iterations if previous iterations haven't completed yet.
Used within a DO / for loop with an ORDERED clause.
The ORDERED directive provides a way to "fine tune" where ordering is to be applied within a loop. Otherwise, it is not required.

Format:

!$OMP DO ORDERED [clauses...]
   (loop region)

!$OMP ORDERED

   (block)

!$OMP END ORDERED

   (end of loop region)
!$OMP END DO

#pragma omp for ordered [clauses...]
   (loop region)

#pragma omp ordered  newline

   structured_block

   (endo of loop region)

An ORDERED directive can only appear in the dynamic extent of the following directives:
- DO or PARALLEL DO (Fortran)
- for or parallel for (C/C++)
Only one thread is allowed in an ordered section at any time.
It is illegal to branch into or out of an ORDERED block.
An iteration of a loop must not execute the same ORDERED directive more than once, and it must not execute more than one ORDERED directive.
A loop which contains an ORDERED directive, must be a loop with an ORDERED clause.