Found no facets matching domain for boundary condition , newton iteration did not converge

Question

I just want to understand the cause of the error . What I got from the error message is that the newton iterations are not converging . What could be the reason for the for this error? Is it because the problem formulation is wrong. Also I got the error "Found no facets matching domain for boundary condition." Is this error due to improper boundary conditions ? Or these errors are due to some fundamental mistake I am doing in writing the code. Please let me know.

from dolfin import *
import numpy, sys

# create mesh
mesh = UnitSquare(5,5)

V = FunctionSpace(mesh,"Lagrange",1) # Function space for u ( Temperature)
Q = FunctionSpace(mesh,"Lagrange",1)  # Function space for \mu ( materi#property
L = FunctionSpace(mesh,"Lagrange",1)  # Function space for \lembda 


M = MixedFunctionSpace([V,Q,L]) # M is mixed function space

# Define the test function space
TestFunction = TestFunction(M)
(v,q,w) = split(TestFunction)

# split the mixed function space into components
# Define the trial function space
solution = Function(M)
(u,mu,lmd) = split(solution)
PrescribedU=Expression("0.25*(pow(x[0],2)+pow(x[1],2))-x[0]*x[1]*0.5-x[0]+0.5*x[1]")

# projecting analytical solution on the function space
u_m = interpolate(PrescribedU,V)

F=inner(nabla_grad(lmd),nabla_grad(v))*mu*dx \
        +inner(nabla_grad(lmd),nabla_grad(u))*q*dx\
        +inner(nabla_grad(w),nabla_grad(u))*mu*dx+inner(v,u-u_m)*dx

def boundary_u(x,on_boundary):
    on_boundary and (near(x[0],0.0) or near(x[0],1.0) \
            or near(x[1],0.0) or near(x[1],1.0))

def boundary_lmd(x,on_boundary):
    on_boundary and (near(x[0],0.0) or near(x[0],1.0) \
            or near(x[1],0.0) or near(x[1],1.0))

# \mu boundaries
def boundary_mu(x,on_boundary):
    on_boundary and (near(x[1],0.0) or near(x[0],1.0))

# u is prescribed on entire boundary
bcs_u = DirichletBC(M.sub(0),PrescribedU , boundary_u)
# \mu prescribed where vector(a).vector(n) < 0 ,i.e inflow boudaries
# inflow boundaries are x[0]=1. and x[1]=0.
# a = Expression("0.5*(x[0]-x[1])-1","(x[1]-x[0])*0.5+0.5")
PrescribedMU= Expression("(2/(exp(2)-1))*(exp(2*x[0])+2*x[1])")
bcs_mu=DirichletBC(M.sub(1),PrescribedMU,boundary_mu)

# \lmd is 0. on entire boundary
bcs_lmd=DirichletBC(M.sub(2),Constant(0.0),boundary_lmd)

bcs=[bcs_u ,bcs_mu , bcs_lmd]


#solution = Function(M)
solve(F==0,solution, bcs)

Error message is as follows:

Newton iteration 6: r (abs) = nan (tol = 1.000e-10) r (rel) = nan (tol = 1.000e-09)
Warning: Found no facets matching domain for boundary condition.
Warning: Found no facets matching domain for boundary condition.

[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Floating point exception!
[0]PETSC ERROR: Infinite or not-a-number generated in norm!
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.2.0, Patch 5, Sat Oct 29 13:45:54 CDT 2011
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Unknown Name on a linux-gnu named linuxGeek by mohit Mon Jan 6 17:05:55 2014
[0]PETSC ERROR: Libraries linked from /build/buildd/petsc-3.2.dfsg/linux-gnu-c-opt/lib
[0]PETSC ERROR: Configure run at Tue Dec 4 14:42:55 2012

Error: Unable to solve nonlinear system with NewtonSolver.
Reason: Newton solver did not converge. Bummer.
Where: This error was encountered inside NewtonSolver.cpp.
Process: 0

Jan Blechta · Answer 1 · Jan 6, 2014

"Found no facets matching domain for boundary condition."

This is a coding error - you're missing return keyword

def boundary_u(x,on_boundary):
    return on_boundary and (near(x[0],0.0) or near(x[0],1.0) \
            or near(x[1],0.0) or near(x[1],1.0))

def boundary_lmd(x,on_boundary):
    return on_boundary and (near(x[0],0.0) or near(x[0],1.0) \
            or near(x[1],0.0) or near(x[1],1.0))

# \mu boundaries
def boundary_mu(x,on_boundary):
    return on_boundary and (near(x[1],0.0) or near(x[0],1.0))

Then Newton solver fails because of infinity in second iteration hence your problem is probably singular.

Found no facets matching domain for boundary condition , newton iteration did not converge

1 Answer