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[Christian Clason <question149919@xxxxxxxxxxxxxxxxxxxxx>]

Question #149919 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/149919

Christian Clason posted a new comment:
Just a small update: The problem seems to be indeed with
PETScKrylovSolver, since PETScKrylovMatrix by itself works fine even
with standard vectors:

from dolfin import *

def boundary(x,on_boundary):
    return on_boundary

mesh = UnitSquare(32, 32)
V = FunctionSpace(mesh, 'CG', 1)

u0 = Constant(0.0)
bc = DirichletBC(V, u0, boundary)
u = TrialFunction(V)
v = TestFunction(V)
a = inner(grad(u), grad(v))*dx

class NewtonMatrix(PETScKrylovMatrix) :
    def __init__(self) :
        PETScKrylovMatrix.__init__(self, V.dim(), V.dim())

    def mult(self, *args) :  
        du = Function(V,args[0])
        f = du*v*dx
        problem = VariationalProblem(a, f, bc)
        dy = problem.solve()
        args[1][:] = dy.vector()[:]

H = NewtonMatrix()

y = Function(V)
b = project(Constant(1.0),V)

H.mult(b.vector(),y.vector())
print(y.vector().norm('l2'))

However,

NewtonSolver = PETScKrylovSolver('cg', 'none')
NewtonSolver.solve(H, b.vector(), y.vector())

throws the error

TypeError: in method 'PETScKrylovSolver_solve', argument 3 of type
'dolfin::PETScVector &'

Christian

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