I am having a strange problem with the gmres solver using the
uBLAS backend. The strange part is that it works fine sometimes,
and fails others, with the same code.
A simple code that demonstrates the problem is:
from dolfin import *
parameters["linear_algebra_backend"] = "PETSc"
mesh = UnitSquare(3,3)
V = FunctionSpace(mesh, 'CG', 1)
v = TestFunction(V)
u = TrialFunction(V)
a = u*v*dx
A = assemble(a)
L = v*dx
b = assemble(L)
x = Vector(b.size())
solve(A, x, b)
print x.array()
Here I run it and get the expected output:
: vinh512 1032; python solve3.py
Warning: Converting real-valued parameter to double, might loose precision.
Warning: Converting real-valued parameter to double, might loose precision.
Matrix of size 16 x 16 has 82 nonzero entries.
Sorting sparsity pattern.
Warning: Converting real-valued parameter to double, might loose precision.
Solving linear system of size 16 x 16 (uBLAS Krylov solver).
Krylov solver converged in 5 iterations.
[ 1.00000005 0.99999996 1.00000011 1.00000001 0.99999996 0.99999992
0.99999997 0.99999995 1.00000011 0.99999997 0.99999998 1.00000003
1.00000001 0.99999995 1.00000003 0.99999999]
Then I run it again, and get an error message:
: vinh512 1032; python solve3.py
Warning: Converting real-valued parameter to double, might loose precision.
Warning: Converting real-valued parameter to double, might loose precision.
Matrix of size 16 x 16 has 82 nonzero entries.
Sorting sparsity pattern.
Warning: Converting real-valued parameter to double, might loose precision.
Solving linear system of size 16 x 16 (uBLAS Krylov solver).
Check failed in file /usr/include/boost/numeric/ublas/operation.hpp at
line 260:
norm_1 (v - cv) <= 2 * std::numeric_limits<real_type>::epsilon () *
verrorbound
Traceback (most recent call last):
File "solve3.py", line 12, in <module>
solve(A, x, b, 'gmres')
File
"/home/faculty/arnold/workshop/FEniCS/lib/python2.6/site-packages/dolfin/cpp.py",
line 4169, in solve
return _cpp.solve(*args)
StandardError: internal logic
Searching on the web for the error message came up with this:
http://archives.free.net.ph/message/20081022.224821.1eddeaa9.da.html
where Gunter Winkler suggests "#define BOOST_UBLAS_TYPE_CHECK 0",
but I don't know how to do this from dolfin.
Any ideas what is going on or how to fix?
