This package solves Laplace, initial value and other problems in order to produce the current response on electrodes due to drifting of nearby charge.
About the name: the core Laplace problems are solved in pochoir with
the finite-difference method (FDM). The core operation of FDM is
sometimes described as a “stencil” convolution. The name pochoir
describes a stencil-based art style. No constraint is intended on
your personal pronunciation of “pochoir”.
pochoir installs in the “usual Python way”. Use of pip and a Python
virtual environment is recommended.
python3 -m venv venv source venv/bin/activiate
Or maybe you prefer direnv
echo layout python3 > .envrc direnv allow
To install the base support (no support for GPU, plots, config)
pip install git+https://github.com/brettviren/pochoir.git@HEAD
Or for development
git clone [email protected]:brettviren/pochoir.git cd pochoir pip install -e .
A number of “extra” support is included mostly for PyTorch, numba, or cupy to try to accelerate some bottlenecks on GPU or via multiprocessing.
pip install -e .[torch,cupy,numba,vtk,plots,hdf5]
Additional setup and of course hardware may be needed to use the GPU support.
The pochoir command line user interface provides online help:
pochoirUsage: pochoir [OPTIONS] COMMAND [ARGS]... pochoir command line interface Options: -s, --store PATH File for primary data storage (input and maybe output) -o, --outstore PATH File for output (primary only input) --help Show this message and exit. Commands: bc-interp Interpolate 2D solution into 3D boundary condition domain Produce a "domain" and store it to the named dataset. drift Calculate drift paths. example Generate a boundary and initial array example (try... export-vtk-image Export a dataset to a vtk file of same name fdm Apply finite-difference method. gen Generate initial and boundary value arrays from a... gencfg Generate JSON configuration files from master file. grad Calculate the gradient of a scalar field. induce Calculate induced current. init Initialize a problem with a shape file. ls List the store store move-paths Move paths along offset vector. plot-drift Visualize 2D or 3D paths plot-image Visualize a dataset as 2D image plot-mag Plot magnitude of a vector field plot-quiver Visualize a 2D or 3D vector field as a "quiver" plot. srdot Apply Ramo theorem dot product. starts Store "starting" points. velo Calculate a velocity field from a potential field version Print the version
Of particular note, to avoid having to always provide the -s/--store
option one may set the store via an environment variable:
export POCHOIR_STORE=/path/to/store
Individual commands provide more details on their use:
pochoir fdm --helpUsage: pochoir fdm [OPTIONS]
Apply finite-difference method.
Solve Laplace equation given initial/boundary value arrays to produce a
scalar potential array.
Options:
-i, --initial TEXT Input initial value array
-b, --boundary TEXT Input the boundary array
-e, --edges TEXT Comma separated list of 'fixed' or
'periodic' giving domain edge conditions
--precision FLOAT Finish when no changes larger than precision
--epoch INTEGER Number of iterations before any check
-n, --nepochs INTEGER Limit number of epochs (def: one epoch)
--engine [numpy|numba|torch|cupy|cumba]
The FDM engine to use
-P, --potential TEXT Output array holding solution for potential
-I, --increment TEXT Output array holding increment (error) on
the solution
--help Show this message and exit.
The pochoir command attempts to be simple and accessible. However,
the calculation it performs is not trivial and has many steps. A user
must understand these steps and what pochoir requires.
The documentation to describe these details is in development. For now see:
- ./overview.org gives a conceptual description of the steps that
pochoircalculates. - ./test/test-sandh2d.org a walk through of a full-chain solving a simplified, purely 2D problem.