Use IvyFEM (Finite Element Method Library for .NET) from Python

1.First of all

IvyFEM.dll, a finite element method library for .NET, is under development. It is a library that is supposed to be used in C #, but I found that it could be used from Python, so I will write it as an article.

2. How to call .NET from Python on Windows 10 (Python .NET)

I decided to use Python.NET.

Below, it is assumed that Python is already installed in the Windows environment.

2.1. Installing Python.NET

Execute the following from the command prompt.

py -m pip install pythonnet

3. IvyFEM.dll package

Download the latest package from the IvyFEM page on Github and extract it to your working directory (see How to install the IvyFEM page, VC ++ runtime required). IvyFEM:

When expanded, it will be as follows. 20200909_python_ivyfem_example_files.jpg

4. Call IvyFEM from Python

I tried to solve Poisson's equation in Python.

It takes a square area and imposes a boundary condition with zero potential on the sides. A circular region is taken inside the region, and the potential distribution of the entire region when a charge is applied to that region is calculated. 20200909_python_ivyfem_example_Cad.jpg

import clr

from System import UInt32

from System.Collections.Generic import List, IList

from IvyFEM \
import \
Cad2D, Mesher2D, FEWorld, \
FiniteElementType, \
PoissonMaterial, \
CadElementType, FieldValueType, FieldFixedCad, \

from IvyFEM.Linear \
import \
LapackEquationSolver, LapackEquationSolverMethod, \
IvyFEMEquationSolver, IvyFEMEquationSolverMethod

from OpenTK import Vector2d

cad = Cad2D()

pts = List[Vector2d]()
pts.Add(Vector2d(0.0, 0.0))
pts.Add(Vector2d(1.0, 0.0))
pts.Add(Vector2d(1.0, 1.0))
pts.Add(Vector2d(0.0, 1.0))
lId1 = cad.AddPolygon(pts).AddLId
print("lId1 = " + str(lId1))

lId2 = cad.AddCircle(Vector2d(0.5, 0.5), 0.1, lId1).AddLId
print("lId2 = " + str(lId2))

eLen = 0.05
mesher = Mesher2D(cad, eLen)

#See coordinates
vecs = mesher.GetVectors()
cnt = len(vecs)
print("len(vecs) = " + str(cnt))
coId = 0
for vec in vecs:
	print("vec[" + str(coId) + "] " + str(vec.X) + ", " + str(vec.Y))
	coId += 1

world = FEWorld()
world.Mesh = mesher

dof = 1 #scalar
feOrder = 1
quantityId = world.AddQuantity(dof, feOrder, FiniteElementType.ScalarLagrange)

ma1 = PoissonMaterial()
ma1.Alpha = 1.0
ma1.F = 0.0
ma2 = PoissonMaterial()
ma2.Alpha = 1.0
ma2.F = 100.0
maId1 = world.AddMaterial(ma1)
maId2 = world.AddMaterial(ma2)

lId1 = 1
world.SetCadLoopMaterial(lId1, maId1)

lId2 = 2
world.SetCadLoopMaterial(lId2, maId2)

zeroEIds = [1, 2, 3, 4]
zeroFixedCads = List[FieldFixedCad]()
for eId in zeroEIds:
    #Note that it is an overload
	fixedCad = FieldFixedCad.Overloads[UInt32, CadElementType, FieldValueType](eId,CadElementType.Edge,FieldValueType.Scalar)
world.SetZeroFieldFixedCads(quantityId, zeroFixedCads)

zeroFixedCads = world.GetZeroFieldFixedCads(quantityId)
print("len(zeroFixedCads) = " + str(len(zeroFixedCads)))


feIds = world.GetTriangleFEIds(quantityId)
feCnt = len(feIds)
print("feCnt = " + str(feCnt))
for feId in feIds:
	print("feId = " + str(feId))
	triFE = world.GetTriangleFE(quantityId, feId)
	nodeCoIds = triFE.NodeCoordIds
	elemNodeCnt = nodeCoIds.Length
	for iNode in range(elemNodeCnt):
		print("coId[" + str(iNode) + "] = " + str(nodeCoIds[iNode]))

#Poisson equation FEM
FEM = Poisson2DFEM(world)

#Linear solver
solver = LapackEquationSolver()
solver.IsOrderingToBandMatrix = True
solver.Method = LapackEquationSolverMethod.Band
FEM.Solver = solver

solver = IvyFEMEquationSolver()
solver.Method = IvyFEMEquationSolverMethod.NoPreconCG
FEM.Solver = solver


nodeCnt = len(U)
for nodeId in range(nodeCnt):
    coId = world.Node2Coord(quantityId, nodeId)
    value = U[nodeId]
    print(str(nodeId) + " " + str(coId) + " " + "{0:e}".format(value))

5. Run

py -m main2

5. Summary

I solved Poisson's equation from Python using IvyFEM.dll.

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