ffc team mailing list archive

[Marie Rognes <meg@xxxxxxxxx>]

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.

(Just as a sidenote.)

--
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
> >