What is conditional compilation in C?

What is conditional compilation in C?

Conditional compilation is the process of selecting which code to compile and which code to not compile similar to the #if / #else / #endif in C and C++. Any statement that is not compiled in still must be syntactically correct.

What is the _openmp macro?

You can use sentinels to mark specific lines of an XL Fortran program for conditional compilation. This allows you to port code that contains statements that are only valid or applicable in an SMP environment to a non-SMP environment.

What is a critical compiler directive in OpenMP?

OpenMP* Fortran Compiler Directive: Restricts access to a block of code to only one thread at a time.

What is OpenMP in C?

OpenMP is a library for parallel programming in the SMP (symmetric multi-processors, or shared-memory processors) model. When programming with OpenMP, all threads share memory and data. OpenMP supports C, C++ and Fortran. The OpenMP functions are included in a header file called omp. h .

What is #if and #endif in C?

The #if directive, with the #elif, #else, and #endif directives, controls compilation of portions of a source file. If the expression you write (after the #if) has a nonzero value, the line group immediately following the #if directive is kept in the translation unit.

What is ifdef and endif in C?

#ifdef: This directive is the simplest conditional directive. They are executed only if the conditional succeeds. You can nest these in multiple layers, but they must be completely nested. In other words, ‘#endif’ always matches the nearest ‘#ifdef’ (or ‘#ifndef’, or ‘#if’).

What is a section compiler directive in OpenMP?

OpenMP provides compiler directives and clauses that used together control the parallelism of regions of code. The directive keyword specifies the parallel action you want to take place. You can use the following OpenMP directives: parallel. for.

What are OpenMP directives?

OpenMP directives exploit shared memory parallelism by defining various types of parallel regions. Parallel regions can include both iterative and non-iterative segments of program code. Pragmas that let you define the scope of data visibility across threads (#pragma omp threadprivate).

How is OpenMP implemented?

When OpenMP processes a sections directive, it starts a number of threads that execute the section blocks concurrently. The assignment of sections to threads is implementation-specific. There is no restriction between the team size and the number of sections.

Where is OpenMP used?

OpenMP is used extensively for parallel computing in sparse equation solvers in both the shared memory and distributed memory versions of OptiStruct. FEATURES OF OPENMP USED: Parallel loops, synchronizations, scheduling, reduction …

What is Ifdef and Ifndef?

ifdef means “if the following is defined” while ifndef means “if the following is not defined”.

What is #if defined in C?

Description. In the C Programming Language, the #ifdef directive allows for conditional compilation. The preprocessor determines if the provided macro exists before including the subsequent code in the compilation process.

What is the name of conditional compilation in OpenMP?

Conditional Compilation The _OPENMPmacro name is defined by OpenMP-compliant implementations as the decimal constant, yyyymm, which will be the year and month of the approved specification. This macro must not be the subject of a #defineor a #undef preprocessing directive.

How to recognize the OpenMP C / C + + directives?

To enable recognition of the OpenMP directives, specify -mp on the ccor CCcommand line. In addition to directives, the OpenMP C/C++ API describes several library functions and environment variables. Information on the library functions can be found on the omp_lock(3), omp_nested(3), and omp_threads(3)man pages.

What are the OpenMP comments in source code?

• OpenMP directives are comments in source code that specify parallelism for shared-memory parallel (SMP) machines • FORTRAN compiler directives begin with one of the sentinels !$OMP, C$OMP, or *$OMP– use !$OMPfor free-format F90 • C/C++ compiler directives begin with the sentinel #pragma omp

How are the OpenMP directives specified in Fortran?

In Fortran, OpenMP directives are specified by using special comments that are identified by unique sentinels. Also, a special comment form is available for conditional compilation. SVG-Viewer needed. Compilers can therefore ignore OpenMP directives and conditionally compiled code if support of the OpenMP API is not provided or enabled.