Installation Guide

AMReX-Hydro is not a stand-alone code: its routines are compiled together with an application that uses them, with either CMake or GNU Make. In both cases the AMReX-Hydro configuration (dimension, precision, MPI, OpenMP, GPU backend and embedded boundaries) must match that of AMReX.

Building with CMake

AMReX-Hydro defines a CMake object library target, amrex_hydro. An application can add AMReX-Hydro to its own CMake build with add_subdirectory, or AMReX-Hydro can be configured and built on its own against an installed AMReX, as follows.

Install AMReX

Build and install AMReX with CMake as described in Building with CMake in the AMReX documentation. AMReX-Hydro builds its embedded boundary (EB) routines by default (HYDRO_EB, see below), which requires AMReX to be built with EB support, -DAMReX_EB=YES.

Clone and Configure AMReX-Hydro

Download AMReX-Hydro from GitHub by using

git clone https://github.com/AMReX-Fluids/AMReX-Hydro.git

In the AMReX-Hydro folder, create and enter a build directory,
```
mkdir build
cd build
```
Call cmake to configure AMReX-Hydro. Set AMReX_ROOT to the AMReX installation directory so that CMake can find AMReXConfig.cmake, and set CMAKE_INSTALL_PREFIX to the directory to install AMReX-Hydro in. Without it, CMake installs in /usr/local, which usually requires administrator rights. For example,
```
cmake -DAMReX_ROOT=/fullpathto/amrex/installdir \
      -DCMAKE_INSTALL_PREFIX=/fullpathto/AMReX-Hydro/installdir \
      <other configuration options> ..
```
Warning

CMake requires an absolute path for the AMReX_ROOT variable. Therefore, a relative path such as -DAMReX_ROOT=../../amrex/installdir will result in an error because CMake will be unable to find AMReXConfig.cmake.

The AMReX-Hydro configuration options are listed in the table below. CMake checks that the installed AMReX was built with the matching components.

Build and Install AMReX-Hydro

While in the AMReX-Hydro build directory AMReX-Hydro/build, build and install AMReX-Hydro by entering
```
make -j4 install
```
The installation directory now contains the library libamrex_hydro_api in lib, the header files in include, and the CMake package files in lib/cmake/AMReX-Hydro (lib64 instead of lib on some systems). An application can then find AMReX-Hydro with find_package(AMReX-Hydro), setting AMReX-Hydro_ROOT to the installation directory.

CMake Options

Option	Description	Default
HYDRO_SPACEDIM	Dimension of the AMReX build: 2 or 3	3
HYDRO_PRECISION	Floating-point precision of the AMReX build: DOUBLE or SINGLE	DOUBLE
HYDRO_MPI	Enable MPI	YES
HYDRO_OMP	Enable OpenMP	NO
HYDRO_GPU_BACKEND	GPU backend: NONE, SYCL, CUDA or HIP	NONE
HYDRO_EB	Build the EB routines (EBMOL and EBGodunov). Requires AMReX built with EB support. (`HYDRO_NO_EB=YES` is a deprecated alias for `HYDRO_EB=NO`.)	YES
HYDRO_PROJECTIONS	Build the MAC and nodal projections	YES
HYDRO_FFT	Build the FFT-based MAC projection. Requires AMReX built with `AMReX_FFT=ON`	NO

Building with GNU Make

Each AMReX-Hydro directory (BDS, EBGodunov, EBMOL, Godunov, MOL, Projections and Utils) has a Make.package file. With AMReX’s GNU Make system, include the Make.package files of the directories you need and add those directories to the include and source paths, e.g.

include $(AMREX_HYDRO_HOME)/Utils/Make.package
INCLUDE_LOCATIONS += $(AMREX_HYDRO_HOME)/Utils
VPATH_LOCATIONS   += $(AMREX_HYDRO_HOME)/Utils

The EBMOL and EBGodunov sources are only compiled with USE_EB = TRUE, and NO_EB = TRUE disables AMReX-Hydro’s EB support in an EB-enabled build. The FFT-based MAC projection is compiled with USE_FFT = TRUE. The GNUmakefile files in the Tests directory are complete examples.