fenics team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

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 <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?
>
> --
> Anders
>
>
> >    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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