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Building xtb with meson

To build xtb from the source in this repository the meson build system can be used. For a decent Fortran support verson 0.51 of meson or newer is required to build xtb, additionally the default backend ninja is required with version 1.7 or newer.

Getting meson

To install the meson build system first check your package manager for an up-to-date meson version, usually this will also install ninja as dependency. Alternatively you can install the latest version of meson and ninja with pip (or pip3 depending on your system):

pip install meson ninja [--user]

If you prefer conda as a package manage you can install meson and ninja from the conda-forge channel. Make sure to select the conda-forge channel for searching packages.

conda config --add channels conda-forge
conda install meson ninja

Configure Intel Fortran build with MKL

The recommended build for xtb is with Intel Parallel Studio using the Intel Fortran compiler and the Math Kernel Library as default backend. Precompiled, statically linked xtb binaries for Linux are provided at release page. The setup for the linear algebra backend defaults to MKL, therefore, only the compilers have to exported before configuring the build:

export FC=ifort CC=icc
meson setup build --buildtype release --optimization 2

After the configuration step the build can be performed with ninja:

ninja -C build

Note, ninja will by default use all the threads available on your system. If you share the build machine with others it might be helpful to reduce the number of concurrent jobs using the -j flag.

Configure GCC build with OpenBLAS

xtb can also be compiled with GCC version 8 or later. For this example we additonally choose to change the linear algebra backend to OpenBLAS, if you have Intel Parallel Studio installed, you can leave out the last argument to get the MKL backend.

export FC=gfortran CC=gcc
meson setup build --buildtype release --optimization 2 -Dla_backend=openblas

To compile and run xtb with GCC 7 (especially 7.3.0) the source code has to be patched at several placed, for appropriate patches visit the conda-forge feedstock repository. The build system will check if the OpenBLAS library provides LAPACK features as well, if this is not the case it will additionally search for LAPACK. If you are compiling xtb on Darwin platforms, ensure that GCC is the actual GCC and not clang. The build can be performed just like before:

ninja -C build

Testing the build with meson

After successfully building the xtb program ensure that it is working as expected. Run the testsuite with

ninja -C build test

All tests should pass, otherwise open an issue.

Installing xtb with meson

To use xtb in production or to pack a release with precompiled binaries the project should be installed with ninja. The installation prefix defaults to /usr/local on Linux systems, you might want to adjust this first by configuring your build with

meson configure build --prefix $HOME/.local

To perform the actual installation run

ninja -C build install

Depending on the installation prefix and your user rights ninja might ask for the root access to perform the installation.

Advanced configuration of install destinations

The installation uses the default install directories of the meson build system To modify the behaviour configure meson with

meson build \
  --prefix=/usr \
  --bindir=bin \
  --libdir=lib \
  --includedir=include \
  --datadir=share \
  --mandir=man

This will result in a directory structure like

usr
├── bin
│   └── xtb
├── include
│   └── xtb.h
├── lib
│   ├── libxtb.a
│   ├── libxtb.so -> libxtb.so.6
│   ├── libxtb.so.6 -> libxtb.so.6.3.2
│   ├── libxtb.so.6.3.2
│   └── pkgconfig
│       └── xtb.pc
└── share
    ├── man
    │   ├── man1
    │   │   └── xtb.1
    │   └── man7
    │       └── xcontrol.7
    ├── modules
    │   └── modulefiles
    │       └── xtb
    │           └── 6.3.2
    └── xtb
        ├── param_gfn0-xtb.txt
        ├── param_gfn1-xtb.txt
        ├── param_gfn2-xtb.txt
        └── param_ipea-xtb.txt

Optimization Level

By default the compiler optimization should only use -O2, although the program can be safely compiled with -O3 when using Intel compilers. It is known that binaries build with GCC on -O3 will produce wrong results for certain systems. To adjust the optimization level to -O3 use

meson configure build --optimization=3

Linear Algebra Backend

When configuring the build the wanted linear algebra backend can be specified with

meson setup build -Dla_backend=<option>

The following options are available:

backend

linked against

mkl-static

static MKL (default)

mkl

shared MKL

mkl-rt

MKL real time library

openblas

OpenBLAS and if required LAPACK

netlib

BLAS and LAPACK

custom

-Dcustom_libraries=…​

If you are using the MKL provided by conda-forge you have to link against the netlib backend

Extending the meson build

To add new source code it should be sufficient to add the new files in the meson.build file in the respective source directory in the src tree. New directories in the src tree can be included by adding them as subdir to the parent meson.build file. To kinds of source files are distinguished, all sources for the xtb library are included in the srcs variable, while files used exclusively for the executable are stored in the prog list. Source files for the testing are defined in the TESTSUITE/meson.build file together with their tests.