OpenMP* Fortran Compiler Directives

Intel® Fortran provides OpenMP* Fortran compiler directives that comply with OpenMP Fortran Application Program Interface (API) specification Version 1.1 and most of Version 2.0.

To use these directives, you must specify compiler option -openmp (Linux and Mac OS X) or /Qopenmp (Windows).

Options that use OpenMP* are available for both Intel® microprocessors and non-Intel microprocessors, but these options may perform additional optimizations on Intel® microprocessors than they perform on non-Intel microprocessors. The list of major, user-visible OpenMP constructs and features that may perform differently on Intel® microprocessors vs. non-Intel microprocessors includes: locks (internal and user visible), the SINGLE construct, barriers (explicit and implicit), parallel loop scheduling, reductions, memory allocation, thread affinity, and binding.

This section discusses data scope attribute clauses, conditional compilation rules, nesting and binding rules, and the following directives:

ATOMIC directive

Specifies that a specific memory location is to be updated dynamically.
BARRIER directive

Synchronizes all the threads in a team.
CRITICAL directive

Restricts access for a block of code to only one thread at a time.
DO directive

Specifies that the iterations of the immediately following DO loop must be executed in parallel.
FLUSH directive

Specifies synchronization points where the implementation must have a consistent view of memory.
MASTER directive

Specifies a block of code to be executed by the master thread of the team.
ORDERED directive

Specifies a block of code to be executed sequentially.
PARALLEL directive

Defines a parallel region.
PARALLEL DO directive

Defines a parallel region that contains a single DO directive.
PARALLEL SECTIONS directive

Defines a parallel region that contains SECTIONS directives.
PARALLEL WORKSHARE directive

Defines a parallel region that contains a single WORKSHARE directive.
SECTIONS directive

Specifies a block of code to be divided among threads in a team (a worksharing area).
SINGLE directive

Specifies a block of code to be executed by only one thread in a team.
TASK directive

Defines a task region.
TASKWAIT directive

Specifies a wait on the completion of child tasks generated since the beginning of the current task.
THREADPRIVATE directive

Makes named common blocks private to a thread but global within the thread.
WORKSHARE directive

Divides the work of executing a block of statements or constructs into separate units.

The OpenMP parallel directives can be grouped into the categories shown in the following table:

Categories of OpenMP Fortran Parallel Directives
Category	Description
Parallel region	Defines a parallel region: PARALLEL
Task region	Defines a task region: TASK
Work-sharing	Divide the execution of the enclosed block of code among the members of the team that encounter it: DO and SECTIONS
Combined parallel work-sharing	Shortcut for denoting a parallel region that contains only one work-sharing construct: PARALLEL DO and PARALLEL SECTIONS
Synchronization	Provide various aspects of synchronization; for example, access to a block of code, or execution order of statements within a block of code: ATOMIC, BARRIER, CRITICAL, FLUSH, MASTER, ORDERED, and TASKWAIT.
Data Environment	Control the data environment during the execution of parallel constructs: THREADPRIVATE

Note that certain general directives and rules can affect DO loops. For more information, see Rules for General Directives that Affect DO Loops.

Optimization Notice
Intel® Compiler includes compiler options that optimize for instruction sets that are available in both Intel® and non-Intel microprocessors (for example SIMD instruction sets), but do not optimize equally for non-Intel microprocessors. In addition, certain compiler options for Intel® Compiler are reserved for Intel microprocessors. For a detailed description of these compiler options, including the instruction sets they implicate, please refer to "Intel® Compiler User and Reference Guides > Compiler Options". Many library routines that are part of Intel® Compiler are more highly optimized for Intel microprocessors than for other microprocessors. While the compilers and libraries in Intel® Compiler offer optimizations for both Intel and Intel-compatible microprocessors, depending on the options you select, your code and other factors, you likely will get extra performance on Intel microprocessors. While the paragraph above describes the basic optimization approach for Intel® Compiler, with respect to Intel's compilers and associated libraries as a whole, Intel® Compiler may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include Intel® Streaming SIMD Extensions 2 (Intel® SSE2), Intel® Streaming SIMD Extensions 3 (Intel® SSE3), and Supplemental Streaming SIMD Extensions 3 (Intel® SSSE3) instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Intel recommends that you evaluate other compilers to determine which best meet your requirements.

Optimization Notice

Intel® Compiler includes compiler options that optimize for instruction sets that are available in both Intel® and non-Intel microprocessors (for example SIMD instruction sets), but do not optimize equally for non-Intel microprocessors. In addition, certain compiler options for Intel® Compiler are reserved for Intel microprocessors. For a detailed description of these compiler options, including the instruction sets they implicate, please refer to "Intel® Compiler User and Reference Guides > Compiler Options". Many library routines that are part of Intel® Compiler are more highly optimized for Intel microprocessors than for other microprocessors. While the compilers and libraries in Intel® Compiler offer optimizations for both Intel and Intel-compatible microprocessors, depending on the options you select, your code and other factors, you likely will get extra performance on Intel microprocessors.

While the paragraph above describes the basic optimization approach for Intel® Compiler, with respect to Intel's compilers and associated libraries as a whole, Intel® Compiler may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include Intel® Streaming SIMD Extensions 2 (Intel® SSE2), Intel® Streaming SIMD Extensions 3 (Intel® SSE3), and Supplemental Streaming SIMD Extensions 3 (Intel® SSSE3) instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors.

Intel recommends that you evaluate other compilers to determine which best meet your requirements.

OpenMP* Fortran Compiler Directives

See Also