Installation

Requirements

The project currently requires:

A C++23 compiler. The code is tested with GCC 14 and newer, and with Clang 19.
CMake 3.24 or newer. Recent CMake is needed in order to use the shipped presets directly.

Conan 2 is optional, but convenient if you want CMake to install dependencies through the Conan-based presets or through DMRG_PACKAGE_MANAGER=conan. A minimal setup is:

python -m pip install conan
conan profile detect
conan remote add conan-dmrg https://neumann.theophys.kth.se/artifactory/api/conan/conan-dmrg

The conan-dmrg remote is needed in order to fetch the current version of h5pp.

Dependencies

xDMRG++ depends on a number of external libraries for dense and sparse linear algebra, tensor operations, file I/O, and command-line parsing.

Some BLAS, LAPACK and Lapacke implementation. Typical choices are FlexiBLAS, Intel MKL, or OpenBLAS. The CMake variable BLA_VENDOR can be used to guide detection.
Eigen for matrix algebra and tensor operations.
TBLIS for selected tensor contractions.
Arpack for iterative eigenvalue problems.
Arpackpp as a C++ front-end to Arpack.
PRIMME for iterative eigenvalue calculations.
h5pp as the HDF5 wrapper used for simulation output.
CLI11 for command-line parsing.
Backward-cpp for stack traces.

If you use the find dependency mode, these libraries must already be visible to CMake through your environment, your package manager, or explicit hints such as <PackageName>_ROOT.

Quick start with CMake Presets

The recommended way to configure the project is with CMake presets. A preset gives a name to a complete CMake configuration, including the build directory, build type, dependency provider, and toolchain-related settings.

A typical example is release-cmake-flexiblas-native:

git clone git@github.com:DavidAce/xDMRGpp.git
cd xDMRGpp
cmake --list-presets
cmake --preset release-cmake-flexiblas-native
cmake --build --preset release-cmake-flexiblas-native
./build/release-cmake-flexiblas-native/xDMRG++ --config input/default.cfg

The configure step creates the build tree under build/release-cmake-flexiblas-native. After the executable has been built, you can edit input/default.cfg or point --config to another file under input/.

For most users this is the least error-prone way to build the project, because the preset already fixes the generator, build directory, and several toolchain choices.

Automatic Dependency Installation

The CMake variable DMRG_PACKAGE_MANAGER selects how dependencies are found or installed:

Option	Description
`find` (default)	Use CMake’s `find_package` to locate dependencies that are already available in the environment.
`cmake`	Use the CMake dependency provider to download and install dependencies during configure.
`conan`	Use Conan-based dependency resolution. The presets with `conan` in their name also enable the Conan dependency provider.

The find mode is usually the right choice when you manage dependencies with your operating system, Conda, Spack, a site installation on a cluster, or a manually maintained environment. The cmake and conan modes are useful when you want a more self-contained setup.

CMake Options

Pass CMake options as -D<OPTION>=<VALUE> during configure.

Var	Default	Description
`DMRG_PACKAGE_MANAGER`	`find`	Select the automatic dependency manager: `find`, `cmake`, `conan`.
`DMRG_USE_QUADMATH`	`FALSE`	Enable `__float128` from `quadmath.h` for `fLBIT` time evolution.
`DMRG_USE_FLOAT128`	`FALSE`	Enable `std::float128_t` for `fLBIT` time evolution.
`DMRG_ENABLE_FP32`	`ON`	Build explicit instantiations for `fp32`.
`DMRG_ENABLE_FP64`	`ON`	Build explicit instantiations for `fp64`.
`DMRG_ENABLE_FP128`	`ON`	Build explicit instantiations for the `fp128` aliases.
`DMRG_ENABLE_CX32`	`ON`	Build explicit instantiations for `cx32`.
`DMRG_ENABLE_CX64`	`ON`	Build explicit instantiations for `cx64`.
`DMRG_ENABLE_CX128`	`ON`	Build explicit instantiations for the `cx128` aliases.
`DMRG_ENABLE_TBLIS`	`FALSE`	Use TBLIS for selected tensor contractions instead of Eigen.
`DMRG_ENABLE_TESTS`	`FALSE`	Enable unit tests and CTest targets.
`DMRG_BUILD_EXAMPLES`	`FALSE`	Build example programs.
`DMRG_BUILD_TOOLS`	`FALSE`	Build auxiliary tools.
`DMRG_ENABLE_DOCS`	`FALSE`	Build the documentation.
`DMRG_CMAKE_DEBUG`	`FALSE`	Print extra information during CMake configuration.
`EIGEN_USE_THREADS`	`TRUE`	Enable threaded Eigen tensor operations.

In addition, variables such as <PackageName>_ROOT and <PackageName>_DIR can be used to help CMake locate dependencies when DMRG_PACKAGE_MANAGER=find.