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

CUASBUILDDIR=$CUAS_ROOT/CUAS-MPI/cmake-build-debug/

number of MPI processes

NN=4

generate simple input file from example integration test

exact=$CUASBUILDDIR/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 * 365243600" out0.nc forcing.nc

run a simple experiment

cuas=$CUASBUILDDIR/tools/cuas.exe

set-up the solver

TOL="-ksprtol 1e-7 -kspatol 1e-15 -kspmaxit 10000 -kspconvergedusemininitialresidualnorm" export PETSCOPTIONS="-optionsleft -kspinitialguessnonzero -pctype 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

Starting from the CUAS-MPI directory: cmake -B build -DCMAKE_BUILD_TYPE=Release -DPETSC_DIR=<petsc-root-directory> -DNETCDF_DIR=<netcdf-root-directory> cmake --build build cmake --install build --prefix <prefix> You may want to use legacy cmake calls to generate Makefiles and build CUAS-MPI: mkdir build cd build cmake .. -DCMAKE_BUILD_TYPE=Release -DPETSC_DIR=<petsc-root-directory> -DNETCDF_DIR=<netcdf-root-directory> -DCMAKE_INSTALL_PREFIX=<prefix> make make install

CUAS-MPI makes use of the following options: | Option | Default | Description | | --- | :---: |--------------------------------------------------------------------------------------------------------------| | CUAS_ENABLE_TESTS | OFF | Enables targets building tests. | | CUAS_ENABLE_DOCS | OFF | Enables targets building documentation. |

References

CUAS-MPI Applications

• Wolovick, Micheal and Humbert, Angelika and Kleiner, Thomas and Rückamp, Martin Regularization and L-curves in ice sheet inverse models: a case study in the Filchner-Ronne catchment, The Cryosphere, vol. 17, no. 12, pages 5027–5060, 2023.