What is EMFEM?

EMFEM is a parallel C++ program targeted at the forward modeling of 3D frequency-domain geophysical electromagnetic method using adaptive finite element method. The main features of EMFEM including:

Modular design
Support both MT and CSEM
Support Arbitrary anisotropic media
Use unstructured tetrahedral mesh to discretize complex structures including topography and bathymetry
The mesh is automatic refined guided by a goal-oriented error estimator
The linear system is solve by iterative method with AMS preconditioner to minimize the computation time and memory usage
To futher impore the efficiency, the code is paralized using mesh decomposition method

Prerequisites

EMFEM uses several open source libraries, including:

mpich or openmpi
PETSc
- PETSc is a library that supports parallel linear algebra, krylov solvers, preconditioners and many other things. Note that PETSc must be compiled with MUMPS and HYPRE.
Metis
- Metis is a library for partitioning graphs and finite element meshes.
Tetgen
- TetGen is a program to generate tetrahedral meshes of any 3D polyhedral domains. EMFEM uses it to refine mesh adaptively.
Eigen
- Eigen is a C++ template library for linear algebra.
nanoflann
- nanoflann is a C++11 header-only library for building KD-Trees of datasets with different topologies. EMFEM uses it to find the vertex or cell closest to a receiver point efficiently.

The easiest way to install the dependencies of EMFEM is using spack. All the dependencies can be installed with

$ spack install mpi metis tetgen eigen petsc+mumps+hypre+superlu-dist nanoflann

Building

Once installed all the dependencies and unpacked the source code of EMFEM into a directory /path/to/emfem. Then configure, compile emfem with

$ cd /path/to/emfem
$ mkdir build
$ cd build
$ spack load mpi
$ cmake -DCMAKE_BUILD_TYPE=Release \
        -DPETSC_DIR=$(spack location -i petsc) \
        -DTETGEN_DIR=$(spack location -i tetgen) \
        -DNANOFLANN_DIR=$(spack location -i nanoflann) \
        -DEIGEN_DIR=$(spack location -i eigen) \
        -DMETIS_DIR=$(spack location -i metis) ..
$ make

Note that EMFEM has only been tested on Linux and macOS systems. For Windows users, we recommend using WSL1/WSL2 or a virtual machine.

Usage

To run the forward modeling process, the user needs to provide three files: the model file, the data template file, and the configuration file. Then use the flowing command to run emfem:

$ mpirun -np <# of processes> ./emfem -options_file <configuration-file-name>

For more details on the format of these files, please refer to the documentation.

License

EMFEM is distributed under MIT License. Please see the file LICENSE for more details.

Contributing

The users are encouraged to open an issue for any questions or bugs. Pull requests for any enhancement are also wellcomed.

Authors

Ce Qin, Henan Polytechnic University, Email: ce.qin@hpu.edu.cn.
Ning Zhao, Henan Polytechnic University, Email: zhaoning@hpu.edu.cn.
Xuben Wang, Chengdu University of Technology, Email: wxb@cdut.edu.cn.

How to cite EMFEM?

If you publish results made using EMFEM, please consider citing:

QIN Ce, WANG XuBen, ZHAO Ning, 2020. Research on the iterative solver
of linear equations in three-dimensional finite element forward modeling
for frequency domain electromagnetic method[J].
Chinese Journal Of Geophysics (in Chinese), 63(8): 3180–3191. DOI:10.6038/cjg2020N0194.

leftwillow/emfem