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Building and installing DFTB+

If you have problems with the build, you can find suggestions for some frequently occuring scenarios in the Troubleshooting section at the bottom.

Requirements

In order to compile DFTB+, you need the following software components:

  • A Fortran 2003 compliant compiler
  • A C-compiler
  • CMake (version 3.16 or newer)
  • GNU make
  • LAPACK/BLAS libraries (or compatible equivalents)
  • Python (version >= 3.2) for the source preprocessor

Optional extra dependencies

Additionally there are optional requirements for some DFTB+ features:

  • ScaLAPACK (version 2.0 or later) and a Fortran aware MPI framework, if you want to build the MPI-parallelised version of the code.
  • In addition to ScaLAPACK, it is recommended to use the ELSI library for large scale systems (version 2.6.x of the library, with partial support of 2.5.0). If ELSI was compiled with PEXSI included, you will also need a C++ compiler.
  • The ARPACK-ng library if using the excited state DFTB functionality.
  • The MAGMA library for GPU accelerated computation.
  • The PLUMED2 library for metadynamics simulations. If you build DFTB+ with MPI, the linked PLUMED library must be also MPI-aware (and must have been built with the same MPI-framework as DFTB+).

External library requirements

  • Make sure that all external libraries are compiled with the same kind models for the numeric variables (same integer size and floating point precision) as DFTB+. Also, they should preferably have been built with the same compiler and with similar compiler flags to DFTB+. (See the Troubleshooting section for further information.)
  • External libraries in non-standard locations (as is typical on many HPC-systems using environment modules) can only be reliable found by CMake if their library path occurs in the CMAKE_PREFIX_PATH environment variable. Make sure that your CMAKE_PREFIX_PATH environment variable contains all relevant library paths!

Requirements for testing DFTB+

In order to execute the code tests and validate them against precalculated results, you will additionally need:

  • Python (version >= 3.2) with NumPy
  • The Slater-Koster data used in the tests (see below)

Tested build environments

DFTB+ is regularly built and tested for both serial and MPI environments on the following architectures:

Architecture Compiler MPI Ext. libraries Notes
x86_64 / Linux GNU Fortran/C 7.5 OpenMPI 2.1 OpenBlas 0.3.7, ScaLAPACK 2.1 ELSI 2.6.1  
x86_64 / Linux GNU Fortran/C 10.1 OpenMPI 4.0 OpenBlas 0.3.10, ScaLAPACK 2.1 ELSI 2.6.1  
x86_64 / Linux Intel Fortran/C 18.0 MPICH 3.2 MKL 18.0 ELSI 2.6.1  
x86_64 / Linux Intel Fortran/C 19.0 MPICH 3.3 MKL 19.0 ELSI 2.6.1  
x86_64 / Linux NAG Fortran 7.0 GNU C 9.2 MPICH 3.3 OpenBlas 0.3.7 ScaLAPACK 2.1 ELSI 2.5.0  
x86_64 / OS X GNU Fortran/C 8.4 -- OpenBlas 0.3.10 [1]

All builds are also tested with the optional ARPACK-NG 3.7 and PLUMED 2.5 libraries.

Notes:

[1] Only partial testing of the serial version.

Obtaining the source

The source code of the last stable release can be downloaded from the DFTB+ homepage.

Alternatively you can clone the public git repository. The tagged revisions correspond to stable releases, while the default branch contains the latest development version.

git clone https://github.com/dftbplus/dftbplus.git
cd dftbplus

The project uses git-submodules for some external dependencies, which will be automatically retrieved during configuration.

Optional extra components

Some optional software components are not distributed with the DFTB+ source code and are also not retrieved automatically. If these are required, you can download these components by using the get_opt_externals utility, e.g.:

./utils/get_opt_externals

This will download all license compatible optional external components. These include the Slater-Koster (slako) data for testing the compiled code.

If you also wish to download and use any of the optional components which have conflicting licenses (e.g. the DftD3 library), you must explicitly request it:

./utils/get_opt_externals ALL

This will then prompt for confirmation when downloading components with other licenses.

Note: if you include components with conflicting licenses into your compilation of DFTB+, you are only allowed to use the resulting binary for your personal research and are not permitted to distribute it.

For more information see the detailed help for this tool by issuing ./utils/get_opt_externals -h.

Building

Important note: CMake caches its variables in the CMakeCache.txt file in the build folder (e.g. _build/CMakeCache.txt). Make sure to delete this file before re-running CMake if you have changed variables in config.cmake or in the toolchain files in the sys/ folder. (Deleting the CMakeCache.txt file is not necessary if you change a variable via the -D command line option.)

In order to build DFTB+ carry out the following steps:

  • Inspect the config.cmake file and customise the global build parameters. (If you are unsure, leave the defaults as they are.)

  • Invoke CMake to configure the build. Specify the installation destination (e.g. $HOME/opt/dftb+) and pass an arbitrary folder (e.g. _build) for the build and the directory containing the source files (e.g. .) as arguments to CMake. Additionally define your Fortran and C compilers as environment variables, e.g. (in a BASH compatible shell):

    FC=gfortran CC=gcc cmake -DCMAKE_INSTALL_PREFIX=$HOME/opt/dftb+ -B _build .
    

    Based on the detected compilers, the build system will read further settings from a corresponding toolchain file in the sys/ folder. Either from a compiler specific one (e.g. gnu.cmake, intel.cmake, etc.) or the generic one (generic.cmake) if the detected compiler combination does not correspond to any of the specific settings. The selected toolchain is indicated in the CMake output. (The toolchain file selection can be manually overriden by setting the TOOLCHAIN CMake variable.)

    You may adjust any CMake variable defined in config.make or in the toolchain files by either modifying the files directly or by setting (overriding) the variable via the -D command line option. For example, in order to use the MKL-library with the GNU-compiler, you would have to override the LAPACK_LIBRARY variable with the CMake command line argument -D:

    -DLAPACK_LIBRARY="mkl_gf_lp64;mkl_gnu_thread;mkl_core"
    

    When needed, you can specify the complete path to a libray or pass linker options as defined variables, e.g.:

    -DLAPACK_LIBRARY="/opt/openblas/libopenblas.a"
    -DLAPACK_LIBRARY="-Wl,--start-group -lmkl_gf_lp64 -lmkl_gnu_thread -lmkl_core -Wl,--end-group"
    

    By default CMake searches for the external libraries in the paths specified in the CMAKE_PREFIX_PATH environment variable. Make sure that your CMAKE_PREFIX_PATH environment variable is set up correctly and contains all the relevant paths when configuring the project, e.g.

    CMAKE_PREFIX_PATH=/opt/elsi:/opt/custom-openblas cmake [...] -B _build .
    

    Some of the external library finders also offer special _LIBRARY_DIR CMake variables for setting search paths, e.g.

    -DLAPACK_LIBRARY_DIR=/opt/custom-openblas
    

    Setting those variables is not normally necessary, if the right search path is already present in the CMAKE_PREFIX_PATH environment variable.

  • If the configuration was successful, start the build by

    cmake --build _build -- -j
    

    This will compile the code using several threads and showing only the most relevant information.

    If, for debugging purposes, you wish to see the exact compiling commands, you should execute a serial build with verbosity turned on instead:

    cmake --build _build -- VERBOSE=1
    
  • Note: The code can be compiled with distributed memory parallelism (MPI), but for smaller shared memory machines, you may find that the performance is better when using OpenMP parallelism only and an optimised thread aware BLAS library is used.

Testing DFTB+

  • After successful compilation, change to the build folder and execute the code tests:

    pushd _build
    ctest
    popd
    

    You can also run the tests in parallel in order to speed this up. If you use parallel testing, ensure that the number of OpenMP threads is reduced accordingly. As an example, assuming your workstation has 4 cores and you have set up the TEST_OMP_THREADS variable to 2 (in config.cmake), issue

    ctest -j2
    

    for an OpenMP compiled binary running two tests simultaneously, each using 2 cores.

    If you want to test the MPI enabled binary with more than one MPI-process, you should set the TEST_MPI_PROCS variable accordingly.

    Testing with hybrid (MPI/OpenMP) parallelism can be specified by setting both, the TEST_MPI_PROCS and TEST_OMP_THREADS variables, e.g:

    set(TEST_MPI_PROCS "2" CACHE STRING "Nr. of processes used for testing")
    set(TEST_OMP_THREADS "2" CACHE STRING "Nr. of OMP-threads used for testing")
    

    Note that efficient production use of the code in this mode may require process affinity (settings will depend on your specific MPI implementation).

    The TEST_MPI_PROCS and TEST_OMP_THREADS cache variables can be updated or changed also after the compilation by invoking CMake with the appropriate -D options, e.g.:

    cmake -B _build -DTEST_MPI_PROCS=2 -DTEST_OMP_THREADS=2 .
    pushd _build; ctest; popd
    

Installing DFTB+

  • The compiled executables, libraries, module files etc. can be copied into an installation directory by

    cmake --install _build
    

    where the destination directory can be configured by the variable CMAKE_INSTALL_PREFIX (in the config.cmake file). The default location is the _install subdirectory within the build directory.

Using DFTB+ as a library

DFTB+ can be also be used as a library and linked into other simulation software packages. In order to compile the library with its public API, make sure to set the WITH_API option to TRUE in the CMake config file config.cmake. When you install the program, it will also install the DFTB+ library, the C-include file and the Fortran module files, which are necessary for linking DFTB+ with C and Fortran programs.

Linking the library in CMake based builds

This is the prefered way of invoking the DFTB+ library into your project. In CMake based projects you can directly use the CMake export file of DFTB+, which is installed in the lib/cmake/dftbplus/ folder in the installation folder. It exports the target DftbPlus::DftbPlus which you can use to obtain all necessary compiler, include and linking options. Your projects CMakeLists.txt, should like something like below:

project(DftbPlusTest LANGUAGES Fortran C)
find_package(DftbPlus REQUIRED)
add_executable(testprogram testprogram.f90)
target_link(testprogram DftbPlus::DftbPlus)

Note, that this will link all libraries in the correct order, which where compiled during the DFTB+ build (e.g. libdftd3, libnegf, etc.). It will additionally contain target dependencies on the external libraries needed to create standalone applications with DFTB+ (e.g. LAPACK::LAPACK, Scalapack::Scalapack, Arpack::Arpack, Plumed::Plumed, Magma::Magma, etc.). You can either use the CMake find-modules shipped with the DFTB+ source to find those libraries (and to define the corresponding targets) or create your own ones, provided they define the appropriate CMake targets. The ELSI library offers a CMake export file providing the elsi::elsi target. Make sure, that CMake can find this export file if the DFTB+ library was compiled with ELSI support (e.g. by setting up the environment variable CMAKE_PREFIX_PATH correctly).

Linking the library in non-CMake based builds

Depending on the choice of external components and whether you want to link DFTB+ to a C or a Fortran binary, you may need different compilation flags and linker options. You can look up the necessary compiler flags and linker options in the dftbplus.pc pkg-config file, which is usually installed into the lib/pkgconfig folder in the installation directory. You can either inspect the file directly, or use the pkg-config tool:

export PKG_CONFIG_PATH=${PKG_CONFIG_PATH}:DFTBPLUS_INSTALL_FOLDER/lib/pkgconfig
pkg-config --cflags dftbplus   # compilation flags (e.g. include options)
pkg-config --libs dftbplus     # library linking options
pkg-config --static --libs dftbplus   # library linking options for static linking

Note, that the flags and libraries shown are either for linking with Fortran or with C, depending on the value of the configuration option PKGCONFIG_LANGUAGE.

If you compile DFTB+ with ELSI, PLUMED or MAGMA-support, make sure that pkg-config can also find their respective pkconfig files, as those libraries are declared as dependencies in the DFTB+ pkg-config file. For external dependencies without pkg-config files (e.g. mbd, negf) the options for linking those libraries can not be queried via pkg-config and must be added manually.

Generating developer documentation

Developer documentation can be generated using the FORD source code documentation generator by issuing

cd doc/dftb+/ford && ford dftbplus-project-file.md

in the main source directory. The documentation will be created in the doc/dftb+/ford/doc folder.

Developer build instructions

You should avoid customizing the build by directly changing variables in the CMake config files, as your changes may accidently be checked in into the repository. Instead, create a customized CMake config file, where you pre-populate the appropriate cache variables. Then use the -C option to load that file:

FC=gfortran CC=gcc cmake -C custom.cmake -B _build .

The customized config file is read by CMake before the compiler detection stage. If your config file contains toolchain dependent options, consider defining the DFTBPPLUS_TOOLCHAIN environment variable and query it in your config file.

Advanced build configuration (e.g. for packagers)

Controlling the toolchain file selection

You can override the toolchain file, and select a different provided case, passing the -DTOOLCHAIN option with the relevant name, e.g.:

-DTOOLCHAIN=gnu

or by setting the toolchain name in the DFTBPLUS_TOOLCHAIN environment variable. If you want to load an external toolchain file instead of one from the source tree, you can specify the file path with the -DTOOLCHAIN_FILE option

-DTOOLCHAIN_FILE=/some/path/myintel.cmake

or with the DFTBPLUS_TOOLCHAIN_FILE environment variable.

Similarly, you can also use an alternative build config file instead of config.cmake in the source tree by specifying it with the -DBUILD_CONFIG_FILE option or by defining the DFTBPLUS_BUILD_CONFIG_FILE environment variable.

Preventing the download of external sources

Depending on the value of the HYBRID_CONFIG_METHODS configuration variable, some dependencies (e.g. mbd, negf, mpifx, scalapackfx) are automatically downloaded during the configuration phase and built during the DFTB+ build process. If you want to ensure that nothing gets downloaded during the build, pass the variable definition

-DHYBRID_CONFIG_METHODS="Find"

to CMake during the configuration. In this case, CMake will only try to find those dependencies on the system (by searching in the standard system paths and in the locations defined in the environment variable CMAKE_PREFIX_PATH) and stop if some components were not found.

Troubleshooting

  • CMake finds the wrong compiler

    CMake should be guided with the help of the environment variables FC, CC (and eventually CXX) to make sure it uses the right compilers, e.g.

    FC=gfortran CC=gcc cmake [...]
    
  • CMake fails to find a library / finds the wrong version of a library

    In most cases this is due to a misconfigured CMAKE_PREFIX_PATH environment variable. It is essential, that CMAKE_PREFIX_PATH contains all paths (besides default system paths), which CMake should search when trying to find a library. Extend the library path if needed, e.g.

    CMAKE_PREFIX_PATH="/opt/somelib:${CMAKE_PREFIX_PATH}" cmake [...]
    
  • ScaLAPACK detection on Ubuntu 20.4 LTS fails

    The OpenMPI version of ScaLAPACK on Ubuntu 20.4 LTS exports an incorrect CMake config file (as of October 2020), which refers to an non-existent library. Instead, set the library name with the SCALAPACK_LIBRARY variable explicitely, e.g.

    cmake -DSCALAPACK_LIBRARY=scalapack-openmpi [...]
    

    which should fix the problem.

  • My library settings in a "_LIBRARIES" variable are ignored

    In order to be consistent with the naming scheme suggested by the CMake documentation, all library related cache variables have been changed to singular nouns, e.g.

    cmake -DSCALAPACK_LIBRARY=scalapack-openmpi [...]
    

    instead of the previous

    cmake -DSCALAPACK_LIBRARIES=scalapack-openmpi [...]
    
  • Fortran libraries compiled with the Intel compiler can not be linked

    In order to enforce compliance with the Fortran 2003 standard (e.g. allowing the automatic allocation of arrays in expressions), DFTB+ passes the -standard-semantics option to the Intel compiler. All external modern Fortran dependencies (e.g. ELSI) must also be compiled by using the -standard-semantics or the -assume realloc_lhs option to ensure correct linking.