This project aims to combine p4est with OpenAcc and Fortran. The goal is to build a simple and compact code for numerical simulations on quadtrees/octrees, using multiple GPUs.

Installation

Prerequisites

• fypp
• An MPI-compatible C and Fortran compiler
• NVHPC or another OpenACC-compatible compiler for GPU support

Compiling p4est

The p4est library is included as a git submodule. It seems most robust to compile this library using a GCC toolchain. To compile it into p4est/build, the following steps can be used:

1. Get the p4est source code:

    git submodule init
    git submodule update
   

2. Get the sc source code required for p4est:

    cd p4est
    git submodule init
    git submodule update
   

3. Go back to the top folder and execute the build_p4est.sh script with:

    bash build_p4est.sh
   

It is also possible to install p4est in a different location (or through a different method), but then the main Makefile has to be updated accordingly.

Compiling foap4 with NVHPC

Load the NVHPC compilers, so that mpif90 points to nvfortran etc. Then simply execute

make

To see a list of compilation options, use

make help

Included examples

These are compiled under build/bin/, typically as both a 2D and 3D variant. Some notable tests/examples are:

• test_refinement_2/3d: tests mesh refinement, prolongation and restriction
• test_xdmf_writer_2/3d: tests XDMF output
• test_advection_2/3d: simple scalar advection test
• test_euler_2/3d: solves Euler's equations of gas dynamics

Viewing results

There is currently an inconsistency between Visit and Paraview regarding the order of XDMF data. To write output that can be viewed from Paraview, add viewer="paraview" to io_write_grid calls, like:

call io_write_grid(f4, base_name, n_output, viewer="paraview")

Then use the legacy XDMF Reader. For visit no viewer="visit" argument is required, since it is the default. For most of the included test cases, the type of output is controlled by an optional argument, like:

mpirun -np 1 ./build/bin/test_euler_2d -viewer=paraview