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On Linux with Spack

A straightforward way to install MFEM is to use spack.

Installing spack

To install spack on Linux, the first step consists in cloning and loading it into a $SPACK directory (see spack for more details).

Assuming spack is well installed into the $SPACK directory, the following command installs a parallel MFEM, which is all SLOTH requires:

source $SPACK/share/spack/setup-env.sh

spack install mfem+mpi

Optional MFEM features

  • +mumps enables the MUMPS direct solver in SLOTH: spack install mfem+mpi+mumps.
  • For problems with more than about 2 billion unknowns, use 64-bit global indices in HYPRE: spack install mfem+mpi ^hypre+mixedint.

Other MFEM options are accepted (SLOTH reads MFEM's configuration) but are not needed.

Installing a given version of MFEM

The user is free to install a different version of MFEM. By default, the latest release is installed. Otherwise, @<version> must be added to the spec, e.g.: 

spack install mfem@4.9+mpi

Once MFEM is installed, SLOTH can be built using the envSloth.sh shell script. This script loads MFEM, defines several environment variables, and compiles SLOTH.

Build SLOTH using the envSloth.sh shell script

The envSloth.sh shell script cannot be run directly from the root of the SLOTH repository. Users must create a separate build directory to compile SLOTH.

Installing Sympy

Please ensure that Sympy is installed. Sympy is a mandatory prerequisite to build SLOTH as it is used to handle physical properties.

If the system Python cannot be modified, Sympy can also be installed with Spack: 

spack install py-sympy
spack load py-sympy

Once MFEM and Sympy are installed, please run the following commands to build SLOTH:

mkdir build
cd build

bash ../envSloth.sh [OPTIONS]
where [OPTIONS] are: 
Build type (default: --release):
  --release          Release, with -march=native
  --portable         Release without -march=native (generic x86-64 target on x86)
  --debug | --coverage | --optim | --minsizerel | --relwithdebinfo

Dependencies:
  --mfem=DIR         local MFEM build (instead of spack on Linux / Homebrew on macOS)
  --exprtk=DIR       ExprTk (directory containing exprtk.hpp)
  --voro=DIR         Voro++ installation prefix
  --libtorch=DIR     LibTorch installation prefix
  --external=EXT_LIBDIR,EXT_LIBNAME
                     link Sloth with an external library

Other options:
  --shared           build Sloth as a shared library
  --install=DIR      installation directory (default: ../SlothInstall)
  --np=N             number of parallel compilation jobs (default: 4)
  -h | --help        print this help

Everything after "--" is passed unchanged to CMake, e.g.:
  bash ../envSloth.sh --exprtk=../../exprtk -- -DMATOOLS_VERBOSITY_LEVEL_1=ON
The up-to-date list is printed by bash ../envSloth.sh --help.

By default, this command builds a static library of SLOTH with release compiler options.

Building a shared library of SLOTH

The --shared option enables building a shared library of SLOTH. However, the user must ensure that the library type used for MFEM is compatible. Certain combinations of static and shared libraries may require specific compiler options, such as -fPIC.

spack builds a static library of MFEM unless the user enables shared ones (see +shared in the spack command): 

spack install mfem+shared+mpi

The make command within the envSloth.sh script does not compile the tests. To compile tests after SLOTH has been built, run the following command:

make tests -j N

where N is a number of CPUs to use for building the tests in parallel.

Once the tests are compiled, users can verify the build by running all tests with ctest:

ctest -j N

Finally, users can install the SLOTH library, headers, and scripts into the SlothInstall directory by running:

make install

Installing SLOTH in user-defined repository

By default, SLOTH is installed in a SlothInstall directory at the same level as the repository.

Users can specify another directory with the --install option of the envSloth.sh script.

Reinstalling after a dependency change

The installed CMake files (SlothInstall/lib/cmake/Sloth/SlothTargets.cmake) keep the link flags of MFEM at the time SLOTH was built. If MFEM is reinstalled or updated with Spack, SLOTH must be rebuilt and reinstalled from an empty build directory.

Using the installed SLOTH

To build your own programs with the installed SLOTH (find_package(Sloth)) and try the example provided with the installation, see Using an installed SLOTH in your own project.

Alternative: installing SLOTH itself with Spack

SLOTH provides its own Spack package. Spack then installs MFEM and all the dependencies, and SLOTH:

source $SPACK/share/spack/setup-env.sh
spack repo add /path/to/SLOTH/spack_repo
spack install sloth
spack load sloth

See spack info sloth for the versions and variants, and Using an installed SLOTH in your own project to build programs with it.