Compiler Directives

The following table lists available compiler directives.

Some directives may perform differently on Intel® microprocessors than on non-Intel microprocessors.

Each general directive name is preceded by the prefix cDEC$; for example, cDEC$ ALIAS. Each OpenMP* Fortran directive name is preceded by the prefix c$OMP; for example, c$OMP ATOMIC. The c in either can be a c, C, *, or ! in fixed-form source code; only ! in free-form source code.

General Directives

Name

Description

ALIAS

Specifies an alternate external name to be used when referring to external subprograms.

ASSUME_ALIGNED

Specifies that an entity in memory is aligned.

ATTRIBUTES

Applies attributes to variables and procedures.

DECLARE

Generates warning messages for undeclared variables.

DEFINE

Creates a variable whose existence can be tested during conditional compilation.

DISTRIBUTE POINT

Specifies distribution for a DO loop.

ELSE

Marks the beginning of an alternative conditional-compilation block to an IF directive construct.

ELSEIF

Marks the beginning of an alternative conditional-compilation block to an IF directive construct.

ENDIF

Marks the end of a conditional-compilation block.

FIXEDFORMLINESIZE

Sets fixed-form line length. This directive has no effect on freeform code.

FORCEINLINE

Specifies that a routine should be inlined whenever the compiler can do so.

FREEFORM

Uses freeform format for source code.

IDENT

Specifies an identifier for an object module.

IF

Marks the beginning of a conditional-compilation block.

IF DEFINED

Marks the beginning of a conditional-compilation block.

INLINE

Specifies that the routines can be inlined.

INTEGER

Selects default integer size.

IVDEP

Assists the compiler's dependence analysis of iterative DO loops.

LOOP COUNT

Specifies the loop count for a DO loop; this assists the optimizer.

MESSAGE

Sends a character string to the standard output device.

NODECLARE

(Default) Turns off warning messages for undeclared variables.

NOFREEFORM

(Default) Uses standard FORTRAN 77 code formatting column rules.

NOINLINE

Specifies that a routine should not be inlined.

NOPARALLEL

Disables auto-parallelization for an immediately following DO loop.

NOOPTIMIZE

Disables optimizations.

NOPREFETCH

Disables a data prefetch from memory.

NOSTRICT

(Default) Disables a previous STRICT directive.

NOUNROLL

Disables the unrolling of a DO loop.

NOUNROLL_AND_JAM

Disables loop unrolling and jamming.

NOVECTOR1

Disables vectorization of a DO loop.

OBJCOMMENT

Specifies a library search path in an object file.

OPTIMIZE

Enables optimizations.

OPTIONS

Controls whether fields in records and data items in common blocks are naturally aligned or packed on arbitrary byte boundaries.

PACK

Specifies the memory starting addresses of derived-type items.

PARALLEL

Enables auto-parallelization for an immediately following DO loop.

PREFETCH

Enables a data prefetch from memory.

PSECT

Modifies certain characteristics of a common block.

REAL

Selects default real size.

SIMD

Controls SIMD vectorization of loops.

STRICT

Disables Intel® Fortran features not in the language standard specified on the command line.

UNDEFINE

Removes a symbolic variable name created with the DEFINE directive.

UNROLL

Tells the compiler's optimizer how many times to unroll a DO loop.

UNROLL_AND_JAM

Enables loop unrolling and jamming.

VECTOR ALIGNED

Specifies that all data is aligned in a DO loop.

VECTOR ALWAYS

Enables vectorization of a DO loop.

VECTOR NONTEMPORAL1

Directs the compiler to use non-temporal (that is, streaming) stores.

VECTOR NOVECTOR

Disables vectorization of a DO loop.

VECTOR TEMPORAL1

Directs the compiler to use temporal (that is, non-streaming) stores.

VECTOR UNALIGNED

Specifies that no data is aligned in a DO loop.

1i32, i64em

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

For more information on compiler option -openmp (Linux* and Mac OS* X) and /Qopenmp (Windows*), refer to the option description in the Compiler Options reference.

OpenMP Fortran Directives

Name

Description

ATOMIC

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

BARRIER

Synchronizes all the threads in a team.

CRITICAL

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

DO

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

FLUSH

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

MASTER

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

ORDERED

Specifies a block of code to be executed sequentially.

PARALLEL

Defines a parallel region.

PARALLEL DO

Defines a parallel region that contains a single DO directive.

PARALLEL SECTIONS

Defines a parallel region that contains SECTIONS directives.

PARALLEL WORKSHARE

Defines a parallel region that contains a single WORKSHARE directive.

SECTIONS

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

SINGLE

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

TASK

Defines a task region.

TASKWAIT

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

THREADPRIVATE

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

WORKSHARE

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

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.

See Also


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