Doc: Fast, Local Compilation

Workflows for compiling without or with slow internet access or
when working on WarpX and its dependencies at the same time.

Docs/source/developers/local_compile.rst

@@ -0,0 +1,89 @@
+.. _developers-local-compile:
+
+Fast, Local Compilation
+=======================
+
+For simplicity, WarpX :ref:`compilation with CMake <building-cmake>` by default downloads, configures and compiles compatible versions of :ref:`central dependencies <install-dependencies>` such as:
+
+* `AMReX <https://amrex-codes.github.io>`__
+* `PICSAR <https://github.com/ECP-WarpX/picsar>`__
+* `openPMD-api <https://github.com/openPMD/openPMD-api>`__
+* `pyAMReX <https://github.com/AMReX-Codes/pyamrex>`__
+* `pybind11 <https://github.com/pybind/pybind11>`__
+
+on-the-fly, which is called a *superbuild*.
+
+In some scenarios, e.g., when compiling without or with slow internet access or when working on WarpX and its dependencies, other strategies might be preferable.
+In the below workflows, you as the developer need to make sure to use compatible versions of the dependencies you provide.
+
+
+.. _developers-local-compile-src:
+
+Compiling From Local Sources
+----------------------------
+
+This workflow is best for developers that make changes to WarpX, AMReX, PICSAR, openPMD-api and/or pyAMReX at the same time.
+For instance, use this if you add a feature in AMReX and want to try it in WarpX before it is proposed as a pull request for inclusion in AMReX.
+
+Instead of downloading the source code of the above dependencies, one can also use an already cloned source copy.
+For instance, clone these three dependencies to ``$HOME/src``:
+
+.. code-block:: bash
+
+   cd $HOME/src
+
+   git clone https://github.com/ECP-WarpX/WarpX.git warpx
+   git clone https://github.com/AMReX-Codes/amrex.git
+   git clone https://github.com/openPMD/openPMD-api.git
+   git clone https://github.com/ECP-WarpX/picsar.git
+   git clone https://github.com/AMReX-Codes/pyamrex.git
+   git clone https://github.com/pybind/pybind11.git
+
+Now modify the dependencies as needed in their source locations, update sources if you cloned them earlier, etc.
+When building WarpX, :ref:`the following CMake flags <building-cmake-options>` will use the respective local sources:
+
+.. code-block:: bash
+
+   cd src/warpx
+
+   rm -rf build
+
+   cmake -S . -B build  \
+     -DWarpX_PYTHON=ON  \
+     -DWarpX_amrex_src=$HOME/src/amrex          \
+     -DWarpX_openpmd_src=$HOME/src/openPMD-api  \
+     -DWarpX_picsar_src=$HOME/src/picsar        \
+     -DWarpX_pyamrex_src=$HOME/src/pyamrex      \
+     -DWarpX_pybind11_src=$HOME/src/pybind11
+
+   cmake --build build -j 8
+
+
+.. _developers-local-compile-findpackage:
+
+Compiling With Pre-Compiled Dependencies
+----------------------------------------
+
+This workflow is best the fastest to compile WarpX, when you just want to change code in WarpX and have the above central dependencies already made available *in the right configurations* (e.g., w/ or w/o MPI or GPU support) from a :ref:`module system <install-hpc>` or :ref:`package manager <install-dependencies>`.
+
+Instead of downloading the source code of the above central dependencies, or using a local copy of their source, we can compile and install those once and instruct CMake to `find their install locations and configurations <https://hsf-training.github.io/hsf-training-cmake-webpage/09-findingpackages/index.html>`__.
+
+WarpX supports this with :ref:`the following CMake flags <building-cmake-options>`:
+
+.. code-block:: bash
+
+   cd src/warpx
+
+   rm -rf build
+
+   cmake -S . -B build  \
+     -DWarpX_PYTHON=ON  \
+     -DWarpX_amrex_internal=OFF    \
+     -DWarpX_openpmd_internal=OFF  \
+     -DWarpX_picsar_internal=OFF   \
+     -DWarpX_pyamrex_internal=OFF  \
+     -DWarpX_pybind11_internal=OFF
+
+   cmake --build build -j 8
+
+As a background, this is also the workflow how WarpX is built in :ref:`package managers such as Spack and Conda-Forge <install-dependencies>`.

Docs/source/developers/workflows.rst

@@ -10,3 +10,4 @@ Workflows
    testing
    documentation
    checksum
+   local_compile

Docs/source/install/cmake.rst

@@ -147,10 +147,12 @@ Relative paths are also supported, e.g. ``-DWarpX_amrex_src=../amrex``.
 
 Or build against an AMReX feature branch of a colleague.
 Assuming your colleague pushed AMReX to ``https://github.com/WeiqunZhang/amrex/`` in a branch ``new-feature`` then pass to ``cmake`` the arguments: ``-DWarpX_amrex_repo=https://github.com/WeiqunZhang/amrex.git -DWarpX_amrex_branch=new-feature``.
+More details on this :ref:`workflow are described here <developers-local-compile-src>`.
 
 You can speed up the install further if you pre-install these dependencies, e.g. with a package manager.
 Set ``-DWarpX_<dependency-name>_internal=OFF`` and add installation prefix of the dependency to the environment variable `CMAKE_PREFIX_PATH <https://cmake.org/cmake/help/latest/envvar/CMAKE_PREFIX_PATH.html>`__.
 Please see the :ref:`introduction to CMake <building-cmake-intro>` if this sounds new to you.
+More details on this :ref:`workflow are described here <developers-local-compile-findpackage>`.
 
 If you re-compile often, consider installing the `Ninja <https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages>`__ build system.
 Pass ``-G Ninja`` to the CMake configuration call to speed up parallel compiles.

Docs/source/install/dependencies.rst

@@ -12,6 +12,11 @@ Please see installation instructions below.
 - `AMReX <https://amrex-codes.github.io>`__: we automatically download and compile a copy of AMReX
 - `PICSAR <https://github.com/ECP-WarpX/picsar>`__: we automatically download and compile a copy of PICSAR
 
+and for Python bindings:
+
+- `pyAMReX <https://github.com/AMReX-Codes/pyamrex>`__: we automatically download and compile a copy of pyAMReX
+- `pybind11 <https://github.com/pybind/pybind11>`__: we automatically download and compile a copy of pybind11
+
 Optional dependencies include:
 
 - `MPI 3.0+ <https://www.mpi-forum.org/docs/>`__: for multi-node and/or multi-GPU execution