OpenMP* Fortran Compiler Directives

Intel® Fortran supports OpenMP* Fortran compiler directives that comply with OpenMP Fortran Application Program Interface (API) specification 5.0 Version TR4, and some of the directives of the OpenMP Version 5.1 specification.

To use these directives, you must specify compiler option -qopenmp (Linux* and macOS*) or /Qopenmp (Windows*).

OpenMP directives are specially formatted Fortran comment lines embedded in the source file which provide the compiler with hints and suggestions for parallelization, optimization, vectorization, and offloading code to accelerator hardware. The compiler uses the information specified in the directives with compiler heuristic algorithms to generate more efficient code. At times, these heuristics may choose to ignore or override the information provided by a directive. If the directive is ignored by the compiler, no diagnostic message is issued.

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 clauses used in multiple OpenMP* Fortran directives, conditional compilation rules, nesting and binding rules, and the following directives:

• ALLOCATE directive

  Specifies memory allocators to use for object allocation and deallocation. This feature is only available for ifx.

• ATOMIC construct

  Specifies that a specific memory location is to be updated atomically.

• BARRIER directive

  Synchronizes all the threads in a team.

• CANCEL directive

  Requests cancellation of the innermost enclosing region of the type specified, and causes the encountering implicit or explicit task to proceed to the end of the canceled construct.

• CANCELLATION POINT directive

  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.

• CRITICAL construct

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

• DECLARE MAPPER directive

  Declares a user-defined data mapper for derived types and local variables that can subsequently be used in MAP clauses. This feature is only available for ifx.

• DECLARE REDUCTION directive

  Declares a user-defined reduction for one or more types.

• DECLARE REDUCTION directive

  Declares a user-defined reduction for one or more types.

• DECLARE SIMD directive

  Generates a SIMD procedure.

• DECLARE TARGET directive

  Causes the creation of a device-specific version of a named routine that can be called from a target region. This feature is only available for ifx.

• DECLARE VARIANT directive

  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 directive

  Determines if a variant of a base procedure is to be called for a given subroutine or function call. This feature is only available for ifx.

• DISTRIBUTE construct

  Specifies that loop iterations will be executed by thread teams in the context of their implicit tasks.

• DISTRIBUTE PARALLEL DO construct

  Specifies a loop that can be executed in parallel by multiple threads that are members of multiple teams.

• DISTRIBUTE PARALLEL DO SIMD construct

  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 SIMD construct

  Specifies a loop that will be distributed across the primary threads of the teams region. It will be executed concurrently using SIMD instructions.

• DO construct

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

• DO SIMD construct

  Specifies a loop that can be executed concurrently using SIMD instructions.

• FLUSH directive

  Specifies synchronization points where the threads in a team must have a consistent view of memory.

• INTEROP directive

  Identifies a foreign runtime context and identifies runtime characteristics of that context, enabling interoperability with it. This feature is only available for ifx.

• LOOP construct

  Specifies that the iterations of the associated loops can execute concurrently. This feature is only available for ifx.

• MASKED construct

  Specifies a block of code to be executed by the primary thread of the team. This feature is only available for ifx.

• MASKED TASKLOOP construct

  Provides an abbreviated way to specify a TASKLOOP construct inside a MASKED construct. This feature is only available for ifx.

• MASKED TASKLOOP SIMD construct

  Provides an abbreviated way to specify a TASKLOOP SIMD construct inside a MASKED construct. This feature is only available for ifx.

• MASTER construct

  Deprecated; see MASKED. Specifies a block of code to be executed by the master thread of the team.

• MASTER TASKLOOP construct

  Deprecated; provides an abbreviated way to specify a TASKLOOP construct inside a MASTER construct. This feature is only available for ifx.

• MASTER TASKLOOP SIMD construct

  Deprecated; provides an abbreviated way to specify a TASKLOOP SIMDconstruct inside a MASTER construct. This feature is only available for ifx.

• ORDERED directive and construct

  Specifies a block of code that the threads in a team must execute in the natural order of the loop iterations.

• PARALLEL construct

  Defines a parallel region.

• PARALLEL DO construct

  Defines a parallel region that contains a single DO directive.

• PARALLEL DO SIMD construct

  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 construct

  Specifies a shortcut for indicating that a loop or loop nest can execute concurrently across multiple threads. This feature is only available for ifx.

• PARALLEL MASKED construct

  Provides an abbreviated way to specify a MASKED construct inside a PARALLEL construct.This feature is only available for ifx.

• PARALLEL MASKED TASKLOOP construct

  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 construct

  Provides an abbreviated way to specify a MASKED TASKLOOP SIMD construct inside a PARALLEL construct.This feature is only available for ifx.

• PARALLEL MASTER construct

  Deprecated; provides an abbreviated way to specify a MASTER construct inside a PARALLEL construct. This feature is only available for ifx.

• PARALLEL MASTER TASKLOOP construct

  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 construct

  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 construct

  Defines a parallel region that contains a single SECTIONS directive.

• PARALLEL WORKSHARE construct

  Defines a parallel region that contains a single WORKSHARE directive.

• REQUIRES directive

  Lists the features that an implementation must support so that the program compiles and runs correctly. This feature is only available for ifx.

• SCAN directive

  Specifies a scan computation that updates each list item in each iteration of the loop the directive appears in.

• SECTIONS construct

  Specifies that the enclosed SECTION directives define blocks of code to be divided among threads in a team.

• SIMD construct

  Requires and controls SIMD vectorization of loops.

• SINGLE construct

  Specifies a block of code to be executed by only one thread in a team at a time.

• TARGET construct

  Creates a device data environment and executes the construct on the same device. This feature is only available for ifx.

• TARGET DATA construct

  Creates a device data environment for the extent of the region. This feature is only available for ifx.

• TARGET ENTER DATA

  Specifies that variables are mapped to a device data environment. This feature is only available for ifx.

• TARGET EXIT DATA

  Specifies that variables are unmapped from a device data environment. This feature is only available for ifx.

• TARGET PARALLEL construct

  Creates a device data environment in a parallel region and executes the construct on that device.

• TARGET PARALLEL DO construct

  Provides an abbreviated way to specify a TARGET directive containing a PARALLEL DO directive and no other statements.

• TARGET PARALLEL DO SIMD construct

  Specifies a TARGET construct that contains a PARALLEL DO SIMD construct and no other statement.

• TARGET PARALLEL LOOP construct

  Specifies a shortcut for specifying a parallel loop inside a TARGET construct that contains no other statements than the parallel loop. This feature is only available for ifx.

• TARGET SIMD construct

  Specifies a TARGET construct that contains a SIMD construct and no other statement.

• TARGET TEAMS construct

  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 construct

  Creates a device data environment and executes the construct on the same device. It also specifies that loop iterations will be shared among the primary threads of all thread teams in a league created by a TEAMS construct.

• TARGET TEAMS DISTRIBUTE PARALLEL DO construct

  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 construct

  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 construct

  Creates a device data environment and executes the construct on the same device. It also specifies that loop iterations will be shared among the master threads of all thread teams in a league created by a teams construct. It will be executed concurrently using SIMD instructions.

• TARGET TEAMS LOOP construct

  Specifies a shortcut for specifying a TEAMS LOOP construct inside a TEAMS construct that contains no other statements. This feature is only available for ifx.

• TARGET UPDATE directive

  Makes the list items in the device data environment consistent with their corresponding original list items.

• TARGET VARIANT DISPATCH directive

  Conditionally calls a procedure offload variant if the device is free; otherwise, executes the procedure on the host. This feature is only available for ifx.

• TASK construct

  Defines a task region.

• TASKGROUP construct

  Specifies a wait for the completion of all child tasks of the current task and all of their descendant tasks.

• TASKLOOP construct

  Specifies that the iterations of one or more associated DO loops should be executed in parallel using OpenMP* tasks. The iterations are distributed across tasks that are created by the construct and scheduled to be executed.

• TASKLOOP SIMD construct

  Specifies a loop that can be executed concurrently using SIMD instructions and that those iterations will also be executed in parallel using OpenMP* tasks.

• TASKWAIT directive

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

• TASKYIELD directive

  Specifies that the current task can be suspended at this point in favor of execution of a different task.

• TEAMS construct

  Creates a group of thread teams to be used in a parallel region.

• TEAMS DISTRIBUTE construct

  Creates a league of thread teams to execute a structured block in the primary thread of each team. It also specifies that loop iterations will be shared among the primary threads of all thread teams in a league created by a TEAMS construct.

• TEAMS DISTRIBUTE PARALLEL DO construct

  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.

• TEAMS DISTRIBUTE PARALLEL DO SIMD construct

  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 construct

  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 region. The loop will be executed concurrently using SIMD instructions.

• TEAMS LOOP construct

  Specifies a shortcut for specifying a LOOP construct inside a TEAMS construct. This feature is only available for ifx.

• THREADPRIVATE directive

  Makes named common blocks private to each thread, but global within the thread.

• WORKSHARE construct

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

The OpenMP parallel directives can be grouped into the categories. For more information about the categories for these directives, see OpenMP* Directives Summary.