# OpenMP* Directives

This is a summary of the OpenMP* directives supported in the Intel® Fortran Compiler. For detailed information about the OpenMP API, see the OpenMP Application Program Interface Version 5.1 specification, which is available from the OpenMP web site.

In the directive lists below, an OpenMP directive is qualified with the word Directive when the name of the directive is also used for one or more elements besides the directive. For example: FLUSH refers to a directive, a statement, and a subroutine.

## PARALLEL Directive

Use this directive to form a team of threads and execute those threads in parallel.

Directive | Description
--- | ---
PARALLEL Directive (OpenMP) | Defines a parallel region.

## TASKING Directives

Use these directives for deferring execution.

Directive | Description
--- | ---
TASK | Defines a task region.
TASKLOOP | Specifies that the iterations of one or more associated DO loops should be executed using OpenMP tasks. The iterations are distributed across tasks that are created by the construct and scheduled to be executed in parallel by the current team.

## WORKSHARING Directives

Use these directives to share work among a team of threads.

Directive | Description
--- | ---
DO Directive | Identifies an iterative worksharing construct in which the iterations of the associated loop should be divided among threads in a team.
LOOP Directive | Specifies that the iterations of the associated DO loops can execute in any order or concurrently. This feature is only available for ifx.
SECTIONS | Specifies that the enclosed `SECTION` directives define blocks of code to be divided among threads in a team. Each section is executed once by a thread in the team.
SINGLE | Specifies that a block of code is to be executed by only one thread in the team.
WORKSHARE | Divides the work of executing a block of statements or constructs into separate units. It also distributes the work of executing the units to threads of the team so each unit is only executed once.

## SYNCHRONIZATION Directives

Use these directives to synchronize between threads.

Directive | Description
--- | ---
ATOMIC | Ensures that a specific memory location is updated atomically; this prevents the possibility of multiple, simultaneous reading and writing of threads.
BARRIER | Synchronizes all the threads in a team. It causes each thread to wait until all of the other threads in the team have reached the barrier.
CRITICAL Directive | Restricts access to a block of code to only one thread at a time.
FLUSH Directive | Identifies synchronization points at which the threads in a team must provide a consistent view of memory.
MASKED | Specifies a block of code to be executed by the primary thread (thread 0) of the team. This feature is only available for ifx.
MASTER (deprecated, see MASKED) | Specifies a block of code to be executed by the primary thread of the team.
ORDERED | Specifies a block of code that the threads in a team must execute in the natural order of the loop iterations.
TASKGROUP | Specifies a wait for the completion of all child tasks of the current task and all of their descendant tasks.
TASKWAIT | Specifies a wait on the completion of child tasks generated since the beginning of the current task.
TASKYIELD | Specifies that the current task can be suspended at this point in favor of execution of a different task.

## Data Environment Directive

Use this directive to affect the data environment.

Directive | Description
--- | ---
DECLARE MAPPER | Declares a user-defined data mapper for derived types and variables that can subsequently be used in MAP clauses.
THREADPRIVATE | Specifies named common blocks to be private (local) to each thread; they are global within the thread.

## Offload Target Control Directives

Use these directives to control execution on one or more offload targets.

Directive | Description
--- | ---
DECLARE TARGET (ifx) | Specifies named routines and variables that are created or mapped to a device. This feature is only available for ifx.
DECLARE VARIANT (ifx) | Identifies a variant of a base procedure and specifies the context in which this variant is used. This feature is only available for ifx.
DISPATCH (ifx) | Determines if a procedure variant is called for a given subroutine or function call. This feature is only available for ifx.
DISTRIBUTE | Specifies that loop iterations will be distributed among the primary threads of all thread teams in a league created by a teams construct.
INTEROP (ifx) | Identifies a foreign runtime context and identifies runtime characteristics of that context, enabling interoperability with it. This feature is only available for ifx.
REQUIRES (ifx) | Lists the features that an implementation must support so that the program compiles and runs correctly. This feature is only available for ifx.
TARGET Directive (ifx) | Creates a device data environment and executes the construct on that device. This feature is only available for ifx.
TARGET DATA (ifx) | Maps variables to a device data environment for the extent of the region. This feature is only available for ifx.
TARGET ENTER DATA (ifx) | Specifies that variables are mapped to a device data environment. This feature is only available for ifx.
TARGET EXIT DATA (ifx) | Specifies that variables are unmapped from a device data environment. This feature is only available for ifx.
TEAMS (ifx) | Creates a league of thread teams inside a target region to execute a structured block in the primary thread of each team. This feature is only available for ifx.
TARGET UPDATE (ifx) | Makes the list items in the device data environment consistent with their corresponding original list items. This feature is only available for ifx.

## Vectorization Directives

Use these directives to control execution on vector hardware.

Directive | Description
--- | ---
SCAN | Specifies a scan computation that updates each list item in each iteration of an enclosing SIMD loop nest.
SIMD Directive (OpenMP*) | Transforms the loop into a loop that will be executed concurrently using SIMD instructions.
DECLARE SIMD | Generates a SIMD procedure.

## Loop Transformation Directive

Use thia directive to transform or restructure loops.

Directive | Description
--- | ---
UNROLL (ifx) | Partially or fully unrolls a DO loop. This feature is only available for ifx.

## Cancellation Constructs

Directive | Description
--- | ---
CANCEL | Requests cancellation of the innermost enclosing region of the construct specified, and causes the encountering task to proceed to the end of the cancelled construct.
CANCELLATION POINT | Defines a point at which implicit or explicit tasks check to see if cancellation has been requested for the innermost enclosing region of the type specified.

## Memory Space Allocation Directive

Use this declarative directive to allocate memory space. This feature is only available for ifx.

Directive | Description
--- | ---
ALLOCATE | Specifies memory allocators to use for object allocation and deallocation.

## Combined and Composite Directives

Use these directives as shortcuts for multiple directives in sequence. A combined construct is a shortcut for specifying one construct immediately nested inside another construct. A combined construct is semantically identical to that of explicitly specifying the first construct containing one instance of the second construct and no other statements.

A composite construct is composed of two constructs but does not have identical semantics to specifying one of the constructs immediately nested inside the other. A composite construct either adds semantics not included in the constructs from which it is composed or the nesting of the one construct inside the other is not conforming.

Directive | Description
--- | ---
DISTRIBUTE PARALLEL DO1 | Specifies a loop that can be executed in parallel by multiple threads that are members of multiple teams.
DISTRIBUTE PARALLEL DO SIMD1 | Specifies a loop that will be executed in parallel by multiple threads that are members of multiple teams. It will be executed concurrently using SIMD instructions.
DISTRIBUTE SIMD1 | Specifies a loop that will be distributed across the primary threads of the teams region. It will be executed concurrently using SIMD instructions
DO SIMD1 | Specifies a loop that can be executed concurrently using SIMD instructions.
MASKED TASKLOOP | Provides an abbreviated way to specify a TASKLOOP construct inside a MASKED construct. This feature is only available for ifx.
MASKED TASKLOOP SIMD | Provides an abbreviated way to specify a TASKLOOP SIMD construct inside a MASKED construct. This feature is only available for ifx.
MASTER TASKLOOP | Deprecated; provides an abbreviated way to specify a TASKLOOP construct inside a MASTER construct. This feature is only available for ifx.
MASTER TASKLOOP SIMD | Deprecated; provides an abbreviated way to specify a TASKLOOP SIMD construct inside a MASTER construct. This feature is only available for ifx.
PARALLEL DO | Provides an abbreviated way to specify a parallel region containing a single DO directive.
PARALLEL DO SIMD | Specifies a loop that can be executed concurrently using SIMD instructions. It provides a shortcut for specifying a PARALLEL construct containing one SIMD loop construct and no other statement.
PARALLEL LOOP | Provides an abbreviated way to specify a parallel region containing a single LOOP construct. This feature is only available for ifx.
PARALLEL MASKED | Provides an abbreviated way to specify a MASKED construct inside a PARALLEL construct. This feature is only available for ifx.
PARALLEL MASKED TASKLOOP | Provides an abbreviated way to specify a MASKED TASKLOOP construct inside a PARALLEL construct. This feature is only available for ifx.
PARALLEL MASKED TASKLOOP SIMD | Provides an abbreviated way to specify a MASKED TASKLOOP SIMD construct inside a PARALLEL construct. This feature is only available for ifx.
PARALLEL MASTER | Deprecated; provides an abbreviated way to specify a MASTER construct inside a PARALLEL construct. This feature is only available for ifx.
PARALLEL MASTER TASKLOOP | Deprecated; provides an abbreviated way to specify a MASTER TASKLOOP construct inside a PARALLEL construct. This feature is only available for ifx.
PARALLEL MASTER TASKLOOP SIMD | Deprecated; provides an abbreviated way to specify a MASTER TASKLOOP SIMD construct inside a PARALLEL construct. This feature is only available for ifx.
PARALLEL SECTIONS | Provides an abbreviated way to specify a parallel region containing a single SECTIONS directive. The semantics are identical to explicitly specifying a PARALLEL directive immediately followed by a SECTIONS directive.
PARALLEL WORKSHARE | Provides an abbreviated way to specify a parallel region containing a single WORKSHARE directive.
TARGET PARALLEL | Creates a device data environment in a parallel region and executes the construct on that device.
TARGET PARALLEL DO | Provides an abbreviated way to specify a TARGET construct that contains a PARALLEL DO construct and no other statement between them.
TARGET PARALLEL DO SIMD | Specifies a TARGET construct that contains a PARALLEL DO SIMD construct and no other statement between them.
TARGET PARALLEL LOOP | Provides an abbreviated way to specify a TARGET region that contains a single PARALLEL LOOP construct and no other statements. This feature is only available for ifx.
TARGET SIMD | Specifies a TARGET construct that contains a SIMD construct and no other statement between them.
TARGET TEAMS | Creates a device data environment and executes the construct on the same device. It also creates a league of thread teams with the primary thread in each team executing the structured block
TARGET TEAMS DISTRIBUTE | Creates a device data environment and then executes the construct on that device. It also specifies that loop iterations will be distributed among the primary threads of all thread teams in a league created by a TEAMS construct.
TARGET TEAMS DISTRIBUTE PARALLEL DO | Creates a device data environment and then executes the construct on that device. It also specifies a loop that can be executed in parallel by multiple threads that are members of multiple teams created by a TEAMS construct.
TARGET TEAMS DISTRIBUTE PARALLEL DO SIMD | Creates a device data environment and then executes the construct on that device. It also specifies a loop that can be executed in parallel by multiple threads that are members of multiple teams created by a TEAMS construct. The loop will be distributed across the teams, which will be executed concurrently using SIMD instructions.
TARGET TEAMS DISTRIBUTE SIMD | Creates a device data environment and then executes the construct on that device. It also specifies that loop iterations will be distributed among the primary threads of all thread teams in a league created by a teams construct. It will be executed concurrently using SIMD instructions.
TARGET TEAMS LOOP | Provides an abbreviated way to specify a TARGET region that contains a single TEAMS LOOP construct with no other statements. This feature is only available for ifx.
TASKLOOP SIMD 1 | Specifies a loop that can be executed concurrently using SIMD instructions and that those iterations will also be executed in parallel using OpenMP tasks.
TEAMS DISTRIBUTE | Creates a league of thread teams to execute the structured block in the primary thread of each team. It also specifies that loop iterations will be distributed among the primary threads of all thread teams in a league created by a TEAMS construct.
TEAMS DISTRIBUTE PARALLEL DO | Creates a league of thread teams and specifies that the associated loop can be executed in parallel by multiple threads that are members of multiple teams.
TEAMS DISTRIBUTE PARALLEL DO SIMD | Creates a league of thread teams to execute a structured block in the primary thread of each team. It also specifies a loop that can be executed in parallel by multiple threads that are members of multiple teams. The loop will be distributed across the primary threads of the teams region, which will be executed concurrently using SIMD instructions.
TEAMS DISTRIBUTE SIMD | Creates a league of thread teams to execute the structured block in the primary thread of each team. It also specifies a loop that will be distributed across the primary threads of the teams.
TEAMS LOOP | Provides an abbreviated way to specify a TEAMS region that contains a single LOOP construct with no other statements. This feature is only available for ifx.

Footnotes:

1 This directive specifies a composite construct.

Parent topic: OpenMP* Support