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Find, Install, or Uninstall OpenMP

openmp.Rd

Set of functions that seek to identify whether OpenMP was installed, allow OpenMP to be installed, and removing OpenMP.

Usage

is_openmp_installed()

openmp_version()

openmp_install(
  password = base::getOption("macrtools.password"),
  verbose = TRUE,
  configure_makevars = TRUE
)

openmp_uninstall(
  password = base::getOption("macrtools.password"),
  verbose = TRUE,
  configure_makevars = TRUE
)

openmp_test()

Arguments

password

Password for user account to install software. Default is NULL.

verbose

Display messages indicating status

configure_makevars

Automatically configure ~/.R/Makevars with or without OpenMP flags. Default is TRUE.

Details

The openmp_*() suite of functions attempts to locate, install, and uninstall the OpenMP runtime library based on the installed Xcode version. These functions mirror the logic described on the macOS R Project OpenMP page and should be used by advanced users who wish to compile R packages that use OpenMP for parallel processing. They are not required for most users.

OpenMP runtime is downloaded from the R-project repository for macOS and installed to:

  • Library: /usr/local/lib/libomp.dylib

  • Headers:

    • /usr/local/include/omp.h;

    • /usr/local/include/ompt.h;

    • /usr/local/include/omp-tools.h; and,

    • /usr/local/include/ompx.h (added in LLVM 19.1.0).

Note: Apple has explicitly disabled OpenMP support in Xcode compilers, but the runtime library can be installed separately and used with -Xclang -fopenmp compiler flags.

Check if OpenMP is installed

Checks the local file system for whether OpenMP runtime library is installed in the default installation location. Specifically, it checks for the libomp.dylib library file and the omp.h header file, e.g:

# Check if OpenMP library exists
[ -f /usr/local/lib/libomp.dylib ] && echo "Library found" || echo "Library not found"
# Check if OpenMP header files exist
[ -f /usr/local/include/omp.h ] && echo "Headers found" || echo "Headers not found"

Installing OpenMP

The openmp_install() function aims to install the appropriate OpenMP runtime library based on the detected Xcode version.

OpenMP Installation Process

The installation process automatically detects your Xcode version and downloads the corresponding OpenMP runtime from the R-project repository:

VERSION="19.1.0"

# Download the appropriate version
curl -O https://mac.r-project.org/openmp/openmp-${VERSION}-darwin20-Release.tar.gz

# Install to system directories
sudo tar fvxz openmp-${VERSION}-darwin20-Release.tar.gz -C /

Using OpenMP in R Packages

During installation, we will automatically configure your ~/.R/Makevars file to include the necessary compiler flags for OpenMP support.

# macrtools - OpenMP: start
CPPFLAGS += -Xclang -fopenmp
LDFLAGS += -lomp
# macrtools - OpenMP: end

Alternatively, you can manually add the lines to your ~/.R/Makevars file. Or, install packages from command line with:

PKG_CPPFLAGS='-Xclang -fopenmp' PKG_LIBS=-lomp R CMD INSTALL myPackage

Uninstalling OpenMP

The openmp_uninstall() attempts to remove OpenMP from the default installation locations.

We use the R sanitized shell command to remove the installed files:

sudo rm -f /usr/local/lib/libomp.dylib
sudo rm -f /usr/local/include/omp.h
sudo rm -f /usr/local/include/ompt.h
sudo rm -f /usr/local/include/omp-tools.h
sudo rm -f /usr/local/include/ompx.h

Note: ompx.h was included in LLVM 19.1.0 and may not exist in older OpenMP versions.

Testing OpenMP Installation

After installing OpenMP, you can test if it's working by checking the ~/.R/Makevars file for the correct flags and verifying the library signature.

Note: This function does not attempt to compile any code, it only checks the configuration and library signature.

Examples

# Check if OpenMP is installed
is_openmp_installed()
#> [1] FALSE