fenics team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

ok.

--
Anders

On Wed, Jan 30, 2013 at 12:31:25PM +0100, Martin Sandve Alnæs wrote:
>    Yes and yes. The dx() notation is just to be more explicit and
>    distinguish it from the old dx=dx(0) notation. I might add an optional
>    warning for uses like f*dx+g*dx(1), which could be forms intending
>    dx(0) or dx().
>    Martin
>
>    On 30 January 2013 12:15, Anders Logg <[1]logg@xxxxxxxxx> wrote:
>
>    On Wed, Jan 30, 2013 at 09:54:39AM +0100, Martin Sandve Alnæs wrote:
>    >    In addition to integration over the entire domain, explained in
>    another
>    >    post, we have introduced a concept called 'regions' in ufl. For
>    this
>    >    post, assume a single mesh. Support for multiple meshes will get
>    some
>    >    attention in the future.
>    >    The ufl language changes for expressing domain relations is work
>    in
>    >    progress, but some useful features are already possible in trunk.
>    We
>    >    keep the concept of disjoint numbered subdomains, which can be
>    easily
>    >    represented as a single meshfunction in dolfin, having a single
>    integer
>    >    label for each cell. In addition we introduce the concept of a
>    region,
>    >    which is the union of any number of subdomains. Thus regions of
>    one
>    >    domain can be overlapping by including some of the same
>    subdomain(s).
>    >    With some automatic symbolic manipulation in ufl, we can now
>    express
>    >    integrals over overlapping regions with zero additional cost at
>    >    assembly time.
>
>      Nice!
>
>    >    Here's the currently simplest syntax for integrals over regions:
>    >    # Define regions as tuples of subdomain labels
>    >    DL, DM, DR = (1,2), (2,), (2,3) # ***
>
>      I guess 'DM = 2' will also work fine here? It will be passed to
>      dx(DM)
>      so that will result in an integral over subdomain 2.
>
>    >    # Define new measures associated with the interior domains
>    >    dx = Measure("dx")[domains]
>    >    # Make forms for equation
>    >    a = u*v*dx() + alpha*dot(grad(u), grad(v))*dx() # Integrals over
>    entire
>    >    domain
>
>      Is the '()' necessary here in 'dx()'? Will it work with just dx?
>
>    >    L = f*v*dx(DR) + g*v*dx(DL) - (f+g)/2*v*dx(DM) # Integrals over
>    regions
>    >    For the full running code, see this demo in the latest dolfin:
>    >
>    >
>    demo/undocumented/overlapping-regions/python/demo_overlapping-regions.p
>    >    y
>    >    Martin
>
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