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# opencl_fdfd
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**opencl_fdfd** is a 3D Finite Difference Frequency Domain (FDFD)
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solver implemented in Python and OpenCL.
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**Capabilities**
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* Arbitrary distributions of the following:
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* Dielectric constant (epsilon)
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* Magnetic permeabilty (mu)
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* Perfect electric conductor (PEC)
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* Perfect magnetic conductor (PMC)
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* Variable-sized rectangular grids
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* Stretched-coordinate PMLs (complex cell sizes allowed)
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Currently, only periodic boundary conditions are included.
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PEC/PMC boundaries can be implemented by drawing PEC/PMC cells near the edges.
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Bloch boundary conditions are not included but wouldn't be very hard to add.
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The default solver (opencl_fdfd.cg_solver(...)) located in main.py implements
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the E-field wave operator directly (ie, as a list of OpenCL instructions
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rather than a matrix). Additionally, there is a slower (and slightly more
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versatile) solver in csr.py which attempts to solve an arbitrary sparse
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matrix in compressed sparse row (CSR) format using the same conjugate gradient
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method as the default solver. The CSR solver is significantly slower, but can
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be very useful for testing alternative formulations of the FDFD wave equation.
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Currently, this solver only uses a single GPU or other OpenCL accelerator;
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generalization to multiple GPUs should be pretty straightforward
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(ie, just copy over edge values during the matrix multiplication step).
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## Installation
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**Dependencies:**
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* python 3 (written and tested with 3.5)
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* numpy
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* pyopencl
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* jinja2
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* [fdfd_tools](https://mpxd.net/gogs/jan/fdfd_tools)
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Install with pip, via git:
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```bash
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pip install git+https://mpxd.net/gogs/jan/opencl_fdfd.git@release
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```
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## Use
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See the documentation for opencl_fdfd.cg_solver(...)
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(located in main.py) for details about how to call the solver.
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An alternate (slower) FDFD solver and a general gpu-based sparse matrix
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solver is available in csr.py . These aren't particularly well-optimized,
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and something like [MAGMA](http://icl.cs.utk.edu/magma/index.html) would
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probably be a better choice if you absolutely need to solve arbitrary
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sparse matrices and can tolerate writing and compiling C/C++ code.
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