# VHeight does not make sense for BlockMatrix

So i’m running some code to solve a quadratic eigenvalue problem but encountering an error when I run it.

[code]import netgen.gui
from netgen.geom2d import SplineGeometry
from ngsolve import *
import matplotlib.pyplot as plt
import netgen.geom2d as geom2d
from netgen.geom2d import unit_square
import numpy as np

geo = SplineGeometry()
geo.AddCircle( (0.0, 0.0), r=1.0, leftdomain=0, rightdomain=1, bc = “scatterer”)
geo.AddCircle ( (0.0, 0.0), r=1.4, leftdomain=1, rightdomain=2)
geo.AddCircle ( (0.0, 0.0), r=1.9, leftdomain=2, rightdomain=0)
ngmesh = geo.GenerateMesh(maxh=0.02)
mesh = Mesh(ngmesh)

nn=2;
fes = H1(mesh, order=4, complex=True, dirichlet=“dir”)

u = fes.TrialFunction()
v = fes.TestFunction()

k = BilinearForm (fes, symmetric=True)

c = BilinearForm (fes, symmetric=True)
c += 1juv*ds(“outerbnd”)

m = BilinearForm (fes, symmetric=True)
m += (1+nn)uv*dx

k.Assemble()
c.Assemble()
m.Assemble()

I = IdentityMatrix(fes.ndof, complex=False)
II = -1*I
B1 = BlockMatrix([[m.mat, None], [None, I]])
B2 = BlockMatrix([[c.mat, k.mat], [II, None]])

u = GridFunction(fes, multidim=20, name=‘resonances’)
lam = ArnoldiSolver(B2, B1, fes.FreeDofs(), u.vecs, shift=2)
Draw(u)
[/code]
This gives the error message

[code]---------------------------------------------------------------------------
NgException Traceback (most recent call last)
in
42 u = GridFunction(fes, multidim=20, name=‘resonances’)
—> 44 lam = ArnoldiSolver(B2, B1, fes.FreeDofs(), u.vecs, shift=2)
45 Draw(u)
46

NgException: VHeight does not make sense for BlockMatrix
[/code]

Does anyone know how to resolve this error?

Hi,

It might be better to make I and II complex, since m.mat, k.mat, c.mat and u.vecs are complex, but I don’t think the issue is with your code – just that some of the lower level functionality hasn’t been fully implemented yet for the complex case.

The error “VHeight does not make sense for BlockMatrix” occurs in the Python bindings for ArnoldiSolver where the height of the first matrix is checked. Height() maps to Vheight() in basematrix.hpp but is not implemented by BlockMatrix and gives the message in specialmatrix.hpp.

Just to see what would happen, I commented out that Height test to allow the code to proceed. I then got an error in basevector.cpp. There’s a comment indicating the implementation of BlockVector is not complete for complex components.

Best,
Dow