Cedar

The Cedar Framework is a robust, variational multigrid library implementing BoxMG on large scale parallel systems.

The Cedar Framework is a collaborative project between the University of Illinois at Urbana-Champaign and Los Alamos National Laboratory. Work on this project is based in part upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0002374.

Cedar is release under the BSD-3-Clause (see LICENSE.txt).

Installation

mkdir build
cd build
ccmake ..

1. [c] to configure. As a basic build, use

   • CMAKE_INSTALL_PREFIX as ./local_install/
   • MPI_LIBRARY is set correctly

2. [c] to configure again

3. [g] to generate

4. make to compile (or make -j4 to compile with 4 threads)

5. make install

CMAKE Options

CMAKE Option	Description
ENABLE_3D	Build with 3D support
ENABLE_EXAMPLES	Build examples
ENABLE_MPI	Build with MPI support
ENABLE_UNIT_TESTS	Build unit tests

Examples

Following the installation instructions above, run the following from the build directory:

• ./examples/ser-poisson-2d or
• mpirun -np 4 ./examples/mpi-poisson-2d

This should give:

Iteration 0 relative l2 norm: 0.388629
Iteration 1 relative l2 norm: 0.0443548
Iteration 2 relative l2 norm: 0.00494131
Iteration 3 relative l2 norm: 0.000513399
Iteration 4 relative l2 norm: 5.44908e-05
Iteration 5 relative l2 norm: 5.60612e-06
Iteration 6 relative l2 norm: 5.86933e-07
Iteration 7 relative l2 norm: 6.04942e-08
Iteration 8 relative l2 norm: 6.30975e-09
Iteration 9 relative l2 norm: 6.52713e-10
Solution norm: 2.04592e-05
Finished Test

The examples above are defined in examples/2d/ser and examples/2d/mpi of the root Cedar directory.

Usage

• The config.json file lists the main configuration settings for the solver.
• src/config/schema.json describes the full set of options.
• Adding "log": ["status","error","info","debug"] to the config.json file will give verbose output.

To view the solution, modify the poisson.cc file to include

    int rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    std::ofstream outfile("solution-"+std::to_string(rank)+".txt");
    outfile << sol;
    outfile.close();

Then make. Here there will be np different solution files solution-*.txt. This can be viewed in Python for example in example_output.ipynb, which gives the following for the processor layout (mpirun -np 6) and the solution:

Citing

@misc{cedar,
  author = {David Moulton and Luke N. Olson and Andrew Reisner},
  title = {Cedar Framework},
  year = {2017},
  url = {https://github.com/cedar-framework/cedar},
  note = {Version 0.1},
}

Getting Help

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