assemble a bilinear form returns a vector

Question

The following minimal example doesn't work
because the assembled bilinearform A is of type

<class 'dolfin.cpp.la.Vector'>

Why? How can I fix this?

The code reads:

from dolfin import *
mesh = UnitSquareMesh(20, 20)
U = FunctionSpace(mesh, "CG", 1)
u = Function(U)
v = TestFunction(U)

rhs = Constant(1.)
bc = DirichletBC(U, 0. , "on_boundary")

A = assemble(inner(grad(u), grad(v))*dx)
b = assemble(rhs*v*dx)
bc.apply(A, b)
solve(A, u.vector(), b)

Answer 1

I think you got your Functions and TrialFunctions mixed up

from dolfin import *
mesh = UnitSquareMesh(20, 20)
U = FunctionSpace(mesh, "CG", 1)
u = TrialFunction(U)
v = TestFunction(U)

rhs = Constant(1.)
bc = DirichletBC(U, 0. , "on_boundary")

A = assemble(inner(grad(u), grad(v))*dx)
b = assemble(rhs*v*dx)
bc.apply(A, b)

soln = Function(U)
solve(A, soln.vector(), b)

Comments

thanks, that solves the problem