On 1 February 2010 15:40, Garth N. Wells <gn...@cam.ac.uk> wrote:

Marie Rognes wrote:
Garth N. Wells wrote:
Marie Rognes wrote:

Garth N. Wells wrote:

There seems to be a nasty bug in the quadrature optimisation. I can
compute a result, but it's wrong. I can try to look into it in more
detail later, but I'm using a combination of BDM and P0 functions which
might be enough of a hint for someone.


Could you give a test script?



Below is a script which reproduces a bug when the quadrature
optimisation is turned on. The norm of vectors assembled with and
without using optimisation dffer.


Same problem arises with CG.

This looks like Harish's old bug where:

      un = dot(u0, n)/2.0

does not work, but

   un   = 0.5*dot(u0, n)

does.

It's a strange one. I thought that Kristian had fixed it.

Interesting is that

 un   = dot(u0, n)/2.0
 F    = 1.0/(s0**2 + 1.0)

doesn't work, but

 un   = dot(u0, n)/2.0
 F    = s0**2

does work, as does

 un   = 0.5*dot(u0, n)
 F    = 1.0/(s0**2 + 1.0)
Strange, I would have guess that the  'F' expression in the first example was 
the problem, but that it works in the last example is a mystery. I'll have a 
look at it.

Kristian

Garth

--
Marie

Garth



from dolfin import *

mesh = UnitSquare(3, 3)
n = FacetNormal(mesh)

BDM = FunctionSpace(mesh, "Brezzi-Douglas-Marini", 1)
P0 = FunctionSpace(mesh, "Discontinuous Lagrange", 0)
mixed_space = MixedFunctionSpace([BDM, P0])

# Function spaces and functions
r  = TestFunction(P0)
U0 = Function(mixed_space)
u0, s0 = split(U0)

U0.vector()[:] = 1.0

un   = dot(u0, n)/2.0
F    = 1.0/(s0**2 + 1.0)
L = r*F*un*ds

param0 = {"representation": "quadrature", "optimize": False}
param1 = {"representation": "quadrature", "optimize": True}
print "Vec norm (no opt):   ", assemble(L,
                             form_compiler_parameters=param0).norm("l2")
print "Vec norm (with opt): ", assemble(L,
                             form_compiler_parameters=param1).norm("l2")



--
Marie

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