Useful links:

General instructions

Amber supports Apple's macOS. The instructions below are for installing Amber's prerequisites natively, i.e., without using a package management system. These systems (such as HomeBrew or MacPorts) can simplify the installation of the prerequisites but must be installed themselves. The target OS is Sonoma 14.4.

Install XCode: XCode contains Apple's development tools. To check whether you have it, run the following command in a terminal:

xcode-select -v

If you do not get a response containing the word "version" then install XCode. You can download it from the Mac App Store (just search for "xcode"). After installing XCode, you may need to agree to the license. So run the following command in a terminal:

sudo xcodebuild -license

Then, read through the license (or type q to skip through it), and enter "agree" when prompted. The command above may emit this error:

xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance

First, try ignoring the error by going to the next step (if that doesn't work then we foresee web searching in your future ;-) or else contact the Amber reflector for advice). After licensing, you need to install the command-line tools. Running the following command in the terminal installs the command-line tools:

xcode-select --install

Optionally Install XQuartz: Starting with OS X 10.8, Apple stopped including X11 with their OS. Instead, you have to get the XQuartz program. To check whether you already have it, look in the Utilities folder in Applications. You can download it here. Note: you only need to do this if you wish to use the xleap program, which many users do Not need.

Install gfortran: You will need a Fortran compiler. Apple doesn't supply one, but to check whether you have gfortran, run the following command in a terminal:

gfortran -v

If you do not get a response containing the word "version" then install gfortran. Get it for your macOS version here. Note: gfortran 11.2.0 was used to beta test Amber 22, but using gfortran-12 from HomeBrew (see below) also seems to work.

Update for OSX 13 (Ventura): So far, there are not any Ventura compilers at the site above for Intel CPUs. Try using HomeBrew to install the GNU compilers with the command "brew install gcc". Also be sure that your XCode distribution is up-to-date (.e.g. at Version 14.2 as of December, 2022.)

Install cmake: Amber now builds with the cmake program, which you can get from cmake.org/download/. You will need to put this program in your PATH as well:

export PATH=/Applications/CMake.app/Contents/bin:$PATH

To check whether you have it installed and in your PATH, run the following command in a terminal:

cmake --version

You should get a response containing the word "version".

Install Amber: Now you are ready to proceed with the installation instructions in the Amber manual. Briefly, go to the amber24_src/build folder, and edit and run the run_cmake script. You can follow this by going to the installation directory chosen in the run_cmake script, sourcing the amber.sh script, and typing "make test.serial". There may be a few errors that all look innocuous. The test suite may claim that pysander is not working, but check this yourself: for me (DAC) using python to "import sander" worked fine in spite of the warning in the test suite .

Comments on M2 (OSX_arch64) from Istvan Kolossvary

I have seen some chatter about this on the list, so I'd just like to post the
recipe that worked for me on M2. It turned out to be very simple, but it only
looks simple after lots of iterations. :) Building the serial version is out
of the box, but for some reason moft cannot be built with either internal or
external boost. These are the CMake settings in run_cmake. I just had to
install cmake and gfortran (via brew).

#  For macOS:

  if [ -x /opt/homebrew/bin/cmake ]; then
     cmake=/opt/homebrew/bin/cmake
  else
     cmake=cmake
  fi

  $cmake $AMBER_PREFIX/amber24_src \
    -DCMAKE_INSTALL_PREFIX=$AMBER_PREFIX/amber24_install \
    -DCOMPILER=CLANG  -DBLA_VENDOR=Apple \
    -DDISABLE_TOOLS="moft" \
    -DMPI=FALSE -DCUDA=FALSE -DINSTALL_TESTS=TRUE \
    -DDOWNLOAD_MINICONDA=TRUE \
    2>&1 | tee cmake.log

The MPI version is more challenging, and in my experience I could not get it
to work with either mpich or openmpi that I built inside amber24_src. I always
had trouble with mpi4py. For me the solution was to install both open-mpi and
mpi4py with brew. mpi4py installs open-mpi, but I needed the extra step to get
the necessary links for cmake to work.

brew install open-mpi
brew install mpi4py
ll /opt/homebrew/bin/mpi*
lrwxr-xr-x  1 istvankolossvary  admin  35 Feb  9 00:35
/opt/homebrew/bin/mpic++ -> ../Cellar/open-mpi/5.0.1/bin/mpic++
lrwxr-xr-x  1 istvankolossvary  admin  34 Feb  9 00:35 /opt/homebrew/bin/mpicc
-> ../Cellar/open-mpi/5.0.1/bin/mpicc
lrwxr-xr-x  1 istvankolossvary  admin  35 Feb  9 00:35
/opt/homebrew/bin/mpicxx -> ../Cellar/open-mpi/5.0.1/bin/mpicxx
lrwxr-xr-x  1 istvankolossvary  admin  36 Feb  9 00:35
/opt/homebrew/bin/mpiexec -> ../Cellar/open-mpi/5.0.1/bin/mpiexec
lrwxr-xr-x  1 istvankolossvary  admin  35 Feb  9 00:35
/opt/homebrew/bin/mpif77 -> ../Cellar/open-mpi/5.0.1/bin/mpif77
lrwxr-xr-x  1 istvankolossvary  admin  35 Feb  9 00:35
/opt/homebrew/bin/mpif90 -> ../Cellar/open-mpi/5.0.1/bin/mpif90
lrwxr-xr-x  1 istvankolossvary  admin  36 Feb  9 00:35
/opt/homebrew/bin/mpifort -> ../Cellar/open-mpi/5.0.1/bin/mpifort
lrwxr-xr-x  1 istvankolossvary  admin  35 Feb  9 00:35
/opt/homebrew/bin/mpirun -> ../Cellar/open-mpi/5.0.1/bin/mpirun

ll /opt/homebrew/lib/libmpi*
lrwxr-xr-x  1 istvankolossvary  admin  44 Feb  9 00:35
/opt/homebrew/lib/libmpi.40.dylib ->
../Cellar/open-mpi/5.0.1/lib/libmpi.40.dylib
lrwxr-xr-x  1 istvankolossvary  admin  41 Feb  9 00:35
/opt/homebrew/lib/libmpi.dylib -> ../Cellar/open-mpi/5.0.1/lib/libmpi.dylib
lrwxr-xr-x  1 istvankolossvary  admin  50 Feb  9 00:35
/opt/homebrew/lib/libmpi_mpifh.40.dylib ->
../Cellar/open-mpi/5.0.1/lib/libmpi_mpifh.40.dylib
lrwxr-xr-x  1 istvankolossvary  admin  47 Feb  9 00:35
/opt/homebrew/lib/libmpi_mpifh.dylib ->
../Cellar/open-mpi/5.0.1/lib/libmpi_mpifh.dylib
lrwxr-xr-x  1 istvankolossvary  admin  62 Feb  9 00:35
/opt/homebrew/lib/libmpi_usempi_ignore_tkr.40.dylib ->
../Cellar/open-mpi/5.0.1/lib/libmpi_usempi_ignore_tkr.40.dylib
lrwxr-xr-x  1 istvankolossvary  admin  59 Feb  9 00:35
/opt/homebrew/lib/libmpi_usempi_ignore_tkr.dylib ->
../Cellar/open-mpi/5.0.1/lib/libmpi_usempi_ignore_tkr.dylib
lrwxr-xr-x  1 istvankolossvary  admin  54 Feb  9 00:35
/opt/homebrew/lib/libmpi_usempif08.40.dylib ->
../Cellar/open-mpi/5.0.1/lib/libmpi_usempif08.40.dylib
lrwxr-xr-x  1 istvankolossvary  admin  51 Feb  9 00:35
/opt/homebrew/lib/libmpi_usempif08.dylib ->
../Cellar/open-mpi/5.0.1/lib/libmpi_usempif08.dylib

Then, simply setting -DMPI=TRUE worked fine, both run_cmake and 'make install'
completed without issues.