# FindOpenMP

Finds Open Multi-Processing (OpenMP) support in a compiler:

    find_package(OpenMP [<version>] [COMPONENTS <langs>...] [...])

If the compiler supports OpenMP, the flags required to compile with OpenMP support are returned in variables for the different languages. The variables may be empty if the compiler does not need a special flag to support OpenMP.

Added in version 3.5: Clang support.

## Components

This module supports components that can be specified using the standard syntax:

    find_package(OpenMP [COMPONENTS <langs>...])

Each of these components controls the various languages to search OpenMP support for. The following components are exposed:

`C`

  Added in version 3.10.

`CXX`

  Added in version 3.10.

`Fortran`

  Added in version 3.10.

`CUDA`

  Added in version 3.31.

  The `CUDA` language component is supported when using a CUDA compiler that supports OpenMP on the host.

If no components are specified, module checks for all of them automatically, depending on the enabled languages in the project.

## Imported Targets

This module provides the following Imported Targets:

`OpenMP::OpenMP_<lang>`

  Added in version 3.9.

  Target encapsulating the OpenMP usage requirements for language `<lang>`.

## Input Variables

The following variables may be set to influence this module's behavior:

`OpenMP_RUNTIME_MSVC`

  Added in version 3.30.

  Specify the OpenMP Runtime when compiling with MSVC. If set to a non-empty value, such as `experimental` or `llvm`, it will be passed as the value of the `-openmp:` flag.

## Result Variables

This module defines the following variables:

`OpenMP_FOUND`

  Added in version 3.10.

  Boolean indicating that OpenMP flags for all requested languages were found. If no components are specified, this variable is set to boolean true if OpenMP settings for all enabled languages were detected.

`OpenMP_VERSION`

  Added in version 4.2.

  Minimal version of the OpenMP standard detected among the requested languages, or all enabled languages if no components were specified.

This module will set the following variables per language in the project, where `<lang>` is one of C, CXX, CUDA, or Fortran:

`OpenMP_<lang>_FOUND`

  Added in version 3.9.

  Boolean indicating whether the (requested version of) OpenMP support for `<lang>` was detected.

`OpenMP_<lang>_VERSION`

  Added in version 3.9.

  OpenMP version implemented by the `<lang>` compiler, if available.

`OpenMP_<lang>_VERSION_MAJOR`

  Added in version 3.9.

  Major version of OpenMP implemented by the `<lang>` compiler, if available.

`OpenMP_<lang>_VERSION_MINOR`

  Added in version 3.9.

  Minor version of OpenMP implemented by the `<lang>` compiler, if available.

`OpenMP_<lang>_SPEC_DATE`

  Added in version 3.7.

  Date of the OpenMP specification implemented by the `<lang>` compiler, if available.

  The specification date is formatted as given in the OpenMP standard: `yyyymm` where `yyyy` and `mm` represents the year and month of the OpenMP specification implemented by the `<lang>` compiler.

`OpenMP_<lang>_FLAGS`

  OpenMP compiler flags for `<lang>`, separated by spaces.

`OpenMP_<lang>_INCLUDE_DIRS`

  Added in version 3.16.

  Directories that must be added to the header search path for `<lang>` when using OpenMP.

For linking with OpenMP code written in `<lang>`, the following variables are provided:

`OpenMP_<lang>_LIB_NAMES`

  Added in version 3.9.

  A semicolon-separated list of OpenMP programs libraries for `<lang>`.

`OpenMP_<libname>_LIBRARY`

  Added in version 3.9.

  Location of the individual libraries needed for OpenMP support in `<lang>`. The `<libname>` names are stored in the `OpenMP_<lang>_LIB_NAMES` list.

`OpenMP_<lang>_LIBRARIES`

  Added in version 3.9.

  A list of libraries needed to link with OpenMP code written in `<lang>`.

Specifically for Fortran, the module sets the following variables:

`OpenMP_Fortran_HAVE_OMPLIB_HEADER`

  Added in version 3.9.

  Boolean indicating whether OpenMP is accessible through the `omp_lib.h` Fortran header.

`OpenMP_Fortran_HAVE_OMPLIB_MODULE`

  Added in version 3.9.

  Boolean indicating whether OpenMP is accessible through the `omp_lib` Fortran module.

For some compilers, it may be necessary to add a header search path to find the relevant OpenMP headers. This location may be language-specific. Where this is needed, the module may attempt to find the location, but it can be provided directly by setting the `OpenMP_<lang>_INCLUDE_DIR` cache variable. Note that this variable is an input control to the module. Project code should use the `OpenMP_<lang>_INCLUDE_DIRS` output variable if it needs to know what include directories are needed, or preferably the `OpenMP::OpenMP_<lang>` imported target.

## Examples

Finding OpenMP support and linking the imported target to a project target using the C language component:

    find_package(OpenMP)
    target_link_libraries(project_target PRIVATE OpenMP::OpenMP_C)