Using the OpenMP Compatibility Libraries

This section describes the steps needed to set up and use the OpenMP Compatibility Libraries from the command line. On Windows* systems, you can also build applications compiled with the OpenMP Compatibility libraries in the Microsoft Visual Studio* development environment.

For a summary of the support provided by the Compatibility and Legacy libraries provided with Intel compilers, see OpenMP* Source Compatibility and Interoperability with Other Compilers.

For a list of the options and libraries used by the OpenMP libraries, see OpenMP Support Libraries.

Set up your environment for access to the Intel compiler to ensure that the appropriate OpenMP library is available during linking. On Windows systems, you can either execute the appropriate batch (.bat) file or use the command-line window supplied in the compiler program folder that already has the environment set up. On Linux and Mac OS systems, you can source the appropriate script file (see Invoking the Compiler from the Command Line. Using the ifortvars File to Specify Location of Components.

During C/C++ compilation, ensure the version of omp.h used when compiling is the version provided by that compiler. For example, on Linux systems when compiling with the GNU C/C++ compiler, use the omp.h provided with the GNU C/C++ compiler. Similarly, during Fortran compilation, ensure that the version of omp_lib.h or omp_lib.mod used when compiling is the version provided by that compiler.

The following table lists the commands used by the various command-line compilers for both C and C++ source files.:

The command for the Intel® Fortran compiler is ifort on Linux, Mac OS X, and Windows operating systems.

For information on the OpenMP libraries and options used by the Intel compiler, see OpenMP Support Libraries.

Command-Line Examples, Windows OS

On Windows systems, to use the Compatibility Libraries with Microsoft Visual C++ in the Microsoft Visual Studio* environment, see Using the OpenMP Compatibility Libraries from Visual Studio*.

To compile and link (build) the entire application with one command using the Compatibility libraries, specify the following Intel compiler command:

By default, the Intel compilers perform a dynamic link of the OpenMP libraries. To perform a static link (not recommended), use the /MT option in place of the /MD option above and add the option /Qopenmp-link:static. The Intel compiler option /Qopenmp-link controls whether the linker uses static or dynamic OpenMP libraries on Windows OS systems (default is /Qopenmp-link:dynamic).

When using Microsoft Visual C++ compiler, you should link with the Intel OpenMP compatibility library. You need to avoid linking the Microsoft OpenMP run-time library (vcomp) and explicitly pass the name of the Intel OpenMP compatibility library as linker options (following /link):

Performing a static link is not recommended, but would require use of the /MT option in place of the /MD option above.

You can also use both Intel C++ and Visual C++ compilers to compile parts of the application and create object files (object-level interoperability). In this example, the Intel compiler links the entire application:

The first command produces two object files compiled by Visual C++ compiler, and the second command produces two more object files compiled by Intel C++ Compiler. The final command links all four object files into an application.

Alternatively, the third line below uses the Visual C++ linker to link the application and specifies the Compatibility library libiomp5md.lib at the end of the third command:

The following example shows the use of interprocedural optimization by the Intel compiler on several files, the Visual C++ compiler compiles several files, and the Visual C++ linker links the object files to create the executable:

The first command uses the Intel® C++ Compiler to produce an optimized multi-file object file named ipo_out.obj by default (the /Fe option is not required; see Using IPO). The second command uses the Visual C++ compiler to produce two more object files. The third command uses the Visual C++ cl command to link all three object files using the Intel compiler OpenMP Compatibility library. Performing a static link (not recommended) requires use of the /MT option in place of the /MD option in each line above.

Command-Line Examples, Linux OS and Mac OS X

To compile and link (build) the entire application with one command using the Compatibility libraries, specify the following Intel compiler command:

By default, the Intel compilers perform a dynamic link of the OpenMP libraries. To perform a static link (not recommended), add the option -openmp-link static. The Intel compiler option -openmp-link controls whether the linker uses static or dynamic OpenMP libraries on Linux OS and Mac OS X systems (default is -openmp-link dynamic).

You can also use both Intel C++ icc/icpc and GNU gcc/g++ compilers to compile parts of the application and create object files (object-level interoperability). In this example, the GNU compiler compiles the C file foo.c (the gcc option -fopenmp enables OpenMP support), and the Intel compiler links the application using the OpenMP Compatibility library:

When using GNU gcc or g++ compiler to link the application with the Intel compiler OpenMP compatibility library, you need to explicitly pass the Intel OpenMP compatibility library name using the -l option, the GNU pthread library using the -l option, and path to the Intel libraries where the Intel C++ compiler is installed using the -L option:

You can mix object files, but it is easier to use the Intel compiler to link the application so you do not need to specify the gcc -l option, -L option, and the -lpthread option:

You can mix OpenMP object files compiled with the GNU gcc compiler, the Intel® C++ Compiler, and the Intel® Fortran Compiler. This example uses use the Intel Fortran Compiler to link all the objects:

Note

Alternatively, you could use the Intel compiler to link the application, but need to pass multiple gfortran libraries using the -l options on the link line:

Using the OpenMP Compatibility Libraries from Visual Studio

When using systems running a Windows OS, you can make certain changes in the Visual C++ Visual Studio 2005 development environment to allow you to use the Intel C++ Compiler and Visual C++ to create applications that use the Intel compiler OpenMP Compatibility libraries.

Note

Microsoft Visual C++ must have the symbol _OPENMP_NOFORCE_MANIFEST defined or it will include the manifest for the vcomp90 dlls. While this may not appear to cause a problem on the build system, it will cause a problem when the application is moved to another system that does not have this DLL installed.

Set the project Property Pages to indicate the Intel OpenMP run-time library location:

1. Open the project's property pages in from the main menu: Project > Properties (or right click the Project name and select Properties) .

2. Select Configuration Properties > Linker > General > Additional Library Directories

3. Enter the path to the Intel compiler libraries. For example, for an IA-32 architecture system, enter: < Intel_compiler_installation_path>\IA32\LIB

Make the Intel OpenMP dynamic run-time library accessible at run-time, you must specify the corresponding path:

1. Open the project's property pages in from the main menu: Project > Properties (or right click the Project name and select Properties).

2. Select Configuration Properties > Debugging > Environment

3. Enter the path to the Intel compiler libraries. For example, for an IA-32 architecture system, enter:

PATH=%PATH%;< Intel_compiler_installation_path>\IA32\Bin

Add the Intel OpenMP run-time library name to the linker options and exclude the default Microsoft OpenMP run-time library:

1. Open the project's property pages in from the main menu: Project > Properties (or right click the Project name and select Properties).

2. Select Configuration Properties > Linker > Command Line > Additional Options

3. Enter the OpenMP library name and the Visual C++ linker option /nodefaultlib: