# Installation ## Dependencies LibRPA depends on the following core software components: - a C++ compiler and an MPI library - a Fortran compiler (and MPI support if [`LIBRPA_ENABLE_FORTRAN_BIND`]() is enabled) - BLAS and LAPACK libraries - a ScaLAPACK library - the [GreenX](https://github.com/nomad-coe/greenX) library for minimax time-frequency grids Optionally, LibRPA can also be linked with an external [ELPA](https://elpa.mpcdf.mpg.de/) installation. This is intended for ELPA-backed optimized linear algebra subroutines. To enable the build interface, configure with `-DLIBRPA_USE_EXTERNAL_ELPA=ON -DEXTERNAL_ELPA_DIR=/path/to/elpa`. Alternatively, LibRPA can build a bundled ELPA source release with `-DLIBRPA_USE_BUNDLED_ELPA=ON`. For *GW*, the following packages are additionally required: - [LibRI](https://github.com/abacusmodeling/LibRI) for tensor contractions - [LibComm](https://github.com/abacusmodeling/LibComm), which is required by LibRI for communication of tensor data between processes - [cereal](https://uscilab.github.io/cereal), which is required by LibRI for data serialization LibRI support is enabled by default and can be disabled for an RPA-only build with `-DLIBRPA_USE_LIBRI=OFF`. CUDA and HIP builds additionally require [LibDDLA](https://github.com/userchba/LibDDLA) for distributed GPU linear algebra. A compatible LibDDLA revision is bundled under `thirdparty/LibDDLA`; an external installation can also be supplied through `LIBDDLA_PATH`. The required source dependencies are bundled under the `thirdparty/` directory in current LibRPA releases. ## Download You can obtain the LibRPA code by cloning the GitHub repository: ```bash git clone https://github.com/AESM-Group/LibRPA ``` For commits before `28b7431` (including tag `v0.4.0-gw-benchmark` and older), LibRI and LibComm are included as Git submodules. In this case, initialize the submodules before compiling with LibRI: ```bash cd LibRPA git submodule update --init --recursive ``` The source tree is now ready for compilation. ## Compile To compile LibRPA, you need working compiler and library toolchains for C++, Fortran, MPI, BLAS/LAPACK, and ScaLAPACK. The Intel compilers and Intel MPI together with MKL from Intel oneAPI are often the most straightforward choice. Alternatively, LibRPA can also be built with GCC/GFortran together with an open-source MPI implementation such as [MPICH](https://www.mpich.org) and an open-source ScaLAPACK library [Netlib ScaLAPACK](https://www.netlib.org/scalapack). LibRPA uses CMake as its build system. Ensure that the compilers and required libraries can be found under directories specified by relevant environment variables, and under the root directory of the source tree: ```bash mkdir build cd build cmake .. make -j 4 ``` This searches for the paths of required dependencies, and builds the LibRPA library and the driver executable. After a successful build, the driver executable `chi0_main.exe` and the shared library `src/librpa.so` (`src/librpa.dylib` on macOS, or `src/librpa.a` if `BUILD_SHARED_LIBS` is disabled) can be found in the **build directory**. You can specify the compilers through environment variables when invoking CMake. For example, to use the Intel classic C++ and Fortran compilers: ```bash CXX=mpiicpc FC=mpiifort cmake .. ``` To help CMake find the correct BLAS/LAPACK and ScaLAPACK libraries at link time, you may need to ensure that the corresponding library directories are visible through `LIBRARY_PATH` or `LD_LIBRARY_PATH`. For example, when using MKL: ```bash export LD_LIBRARY_PATH="$MKLROOT/lib/intel64:$LD_LIBRARY_PATH" CXX=mpiicpc FC=mpiifort cmake .. ``` By default, LibRPA builds and links against the bundled GreenX source distributed under thirdparty/greenX. If you want to use an external GreenX instead, you should enable the CMake option [`LIBRPA_USE_EXTERNAL_GREENX`](): ```bash cmake -DLIBRPA_USE_EXTERNAL_GREENX=ON .. ``` In this case, LibRPA does not build the bundled GreenX copy. Instead, the parent or higher-level CMake project must provide the external GreenX target `LibGXMiniMax`. Several build scripts are provided on the [build examples](../examples/build/index) page to help users build LibRPA on different platforms and with different toolchains. You may use them as starting points and adapt them to your local environment. For a complete list of compile options, please refer to the [Compile Options](compile_options) page. ## Troubleshooting ### `std::filesystem` link errors with Intel compilers When building LibRPA with Intel compilers, the final link step may fail with errors similar to ```text undefined reference to `std::filesystem::create_directories(...)' undefined reference to `std::filesystem::status(...)' undefined reference to `std::filesystem::__cxx11::path::_M_split_cmpts()' ``` This is usually not a LibRPA source-code issue. On Linux, Intel compilers use GCC’s C++ standard library, libstdc++. If the compiler wrapper picks up an old system GCC/libstdc++, C++17 `std::filesystem` symbols may be unavailable or may require extra linking. A recommended solution is to use a recent GCC version before configuring and building LibRPA. On HPC, it usually amounts to loading a recent GCC module, for example ```bash module load gcc/13.4.0 ``` Then rerun CMake from a clean build directory. ### ELPA `` macro conflict When compiling LibRPA with external ELPA, C++ compilation may fail after including `elpa/elpa.h` with errors similar to ```text error: expected identifier before '(' token error: expected ']' before '(' token ``` This can happen when `elpa/elpa.h` includes the C header ``, which defines the macro `I`. The macro can then conflict with LibRPA C++ code that uses `I` as a normal variable name. Official ELPA releases up to `2025.01.x` may be affected; `2025.06.001` and newer use a C++ guard so C++ code sees `` instead. The recommended solution is to use ELPA `2025.06.001` or newer. If you must use an affected ELPA version, a local workaround is to patch the installed `elpa/elpa.h` header by replacing ```c #include ``` with ```c #ifdef __cplusplus #include #else #include #endif ``` Then rerun CMake from a clean build directory.