CUAS-MPI ·

What is CUAS-MPI?

CUAS-MPI is an MPI parallel implementation of the Confined-Unconfined Aquifer System model (CUAS18) for subglacial hydrology. The implementation relies on the parallel data structures and linear system solvers provided by the Portable, Extensible Toolkit for Scientific Computation (PETSc). The model uses a one-layer equivalent porous medium (EPM) approach for efficient (channel-like) and inefficient (cavity-like) subglacial water transport. A two-dimensional Darcy-type groundwater flow equation with spatially and temporarily varying hydraulic transmissivity is solved considering confined and unconfined aquifer conditions.

How to use it?

One of the integration tests can be used to generate a simple setup to explore the modelling choices and command line options. The example below needs ncks and ncap2 from the NCO toolkit to manipulate the NetCDF files.

# modifiy according to your installation
CUAS_BUILD_DIR=$CUAS_ROOT/CUAS-MPI/cmake-build-debug/

# number of MPI processes
NN=4

#
# generate simple input file from example integration test
#
exact=$CUAS_BUILD_DIR/test/cuascore/integration/test-exactSteadySolution
mpirun -n $NN $exact 1000.0 101 101 31 86400 out0.nc
# convert output to CUAS-MPI input and forcing file format
ncks -O -d time,-1 -v topg,bnd_mask,thk out0.nc input.nc
ncap2 -O -s "bmelt=watersource * 365*24*3600" out0.nc forcing.nc

# run a simple experiment 
#
cuas=$CUAS_BUILD_DIR/tools/cuas.exe

# set-up the solver
TOL="-ksp_rtol 1e-7 -ksp_atol 1e-15 -ksp_max_it 10000 -ksp_converged_use_min_initial_residual_norm"
export PETSC_OPTIONS="-options_left -ksp_initial_guess_nonzero -pc_type bjacobi -ksp_type gmres $TOL"

# make use of many options for this example
mpirun -n $NN  $cuas --totaltime '15 days' --dt '1 hour' --saveEvery 1 --verbose --outputSize large \
       --doChannels --Tmax 100  --Tmin 1.e-08 --initialHead Nzero  $opts \
       --conductivity 10 --layerThickness 0.1 \
       --flowConstant 3.4e-24 --cavityBeta 5e-4 --basalVelocityIce 1e-6 --supplyMultiplier 1.0 \
       --forcingFile forcing.nc  \
       input.nc output.nc

How to install?

Requirements

• c++ compiler
  • at least support for c++ 17
  • the code is tested using gcc/10.2.0
• MPI
  • we use OpenMPI
    • https://www.open-mpi.org/
    • version 4.0.x and 4.1.x
• PETSc
  • https://petsc.org/
  • we tested version 3.14.6
  • with MPI support
• netcdf-c
  • https://www.unidata.ucar.edu/software/netcdf/
  • we use version 4.7.4
  • with MPI and hdf5 1.8.22

Build

We expect that PETSC_ROOT and LIBNETCDF_ROOT are set, being the path to the toplevel diretory of your PETSc and NetCDF installation. And CUAS_INSTALL_PREFIX is the path which you want to use for the CUAS-MPI installation. Fullfilling these requirements, you should be able to run:

cmake -B build -DCMAKE_BUILD_TYPE=Release -DPETSC_DIR=$PETSC_ROOT -DNETCDF_DIR=$LIBNETCDF_ROOT
cmake --build build
cmake --install build --prefix CUAS_INSTALL_PREFIX

Beside the default cmake options like CMAKE_BUILD_TYPE we use the following options:

Option	Default	Description
BUILD_TESTS	OFF	Enables build of unit and integration tests

References

[CUAS18]

Beyer, Sebastian and Kleiner, Thomas and Aizinger, Vadym and Rückamp, Martin and Humbert, Angelika A confined–unconfined aquifer model for subglacial hydrology and its application to the Northeast Greenland Ice Stream. In The Cryosphere, pages 3931–3947, 2018.