| name | fipy-sim |
| description | Use when driving FiPy (NIST's pure-Python finite-volume PDE solver) via Python scripts — diffusion / transient / convection / reaction PDEs on 1D/2D/3D structured / Gmsh meshes, steady or time-stepping — through sim runtime one-shot execution. |
fipy-sim
You are connected to FiPy via sim-cli.
FiPy is the canonical pure-Python finite-volume PDE solver (NIST,
2003-present). Pip-installable (pip install fipy); pure Python on top
of NumPy/SciPy with optional acceleration via PySparse / PyAMG /
petsc4py / Trilinos.
Scripts are plain .py:
from fipy import CellVariable, Grid1D, TransientTerm, DiffusionTerm
mesh = Grid1D(nx=50, dx=0.02)
phi = CellVariable(name='phi', mesh=mesh, value=0.0)
phi.constrain(1.0, mesh.facesLeft)
phi.constrain(0.0, mesh.facesRight)
eq = TransientTerm() == DiffusionTerm(coeff=1.0)
for _ in range(100):
eq.solve(var=phi, dt=0.01)
Same subprocess driver mode as PyBaMM / PyMFEM / SfePy.
base/ — always relevant
| Path | What's there |
|---|
base/reference/workflow.md | Mesh → variable → BCs → equation → solve / sweep loop. |
base/reference/meshes.md | Grid1D / Grid2D / Gmsh2D, FaceVariable / CellVariable. |
base/reference/terms.md | TransientTerm / DiffusionTerm / ConvectionTerm / Source. |
base/snippets/01_poisson.py | Verified steady-state 1D Poisson E2E. |
base/known_issues.md | Cell-center vs face values, sweep vs solve, sparse solver fallback. |
sdk/4/ — FiPy 4.x
sdk/4/notes.md — version-specific surface notes.
Hard constraints
- Boundary conditions are applied via
.constrain(value, faces),
not by zeroing rows. mesh.facesLeft / facesRight / facesTop / facesBottom
are the standard locators for grid meshes.
- For transient problems, use
TransientTerm() on the LHS:
TransientTerm() == DiffusionTerm(...). Without it, FiPy treats
the equation as steady and ignores dt.
- For nonlinear equations, use
.sweep(var=, dt=) in a loop until
residual converges, not .solve (which does one Newton step only).
- Acceptance != "ran without error". Always validate against an
analytical or benchmark profile (e.g. linear profile for 1D Poisson
with mixed Dirichlet, error function for 1D semi-infinite diffusion).
- Print results as JSON on the last stdout line.
Required protocol
- Gather inputs:
- Category A: PDE, domain, BCs, time span (transient), acceptance.
- Category B: mesh density, time step, solver tolerance.
sim check fipy.- Write
.py per base/reference/workflow.md.
sim lint script.py.sim run script.py --solver fipy.- Validate JSON.
