dolfin team mailing list archive

[Dag Lindbo <dag@xxxxxxxxxx>]

Anders Logg wrote:
> On Thu, May 22, 2008 at 11:26:41AM +0200, Dag Lindbo wrote:
>> DOLFIN wrote:
>>> One or more new changesets pushed to the primary dolfin repository.
>>> A short summary of the last three changesets is included below.
>>>
>>> changeset:   4224:c5a7da38ff2c966e5f2483b5232993fb75ac6aa1
>>> tag:         tip
>>> user:        Anders Logg <logg@xxxxxxxxx>
>>> date:        Thu May 22 10:19:48 2008 +0200
>>> files:       dolfin/fem/DirichletBC.cpp dolfin/fem/DirichletBC.h
>>> description:
>>> Major cleanup of DirichletBC:
>>>  - Store boundary facets in array, common for all different representations
>>>  - BCs may now be specified in 3 differenet ways: SubDomain, MeshFunction, or as Mesh data
>>>  - Should speed up repeated application of BCs
>>>  - Tested on a few different applications, but please check that nothing broke.
>>>    In particular, geometric and pointwise application has not been tested.
>> Noting broke here!
> 
> ok, nice. Thanks for checking (Kristian also).
> 
>> However, I'm not seeing the speedup... (and I'm reapplying the dirichlet
>> bcs every timestep). My code spends a good 30% of runtime applying
>> dirichlet BCs (linear systems are pre-factorized so the solve step takes
>> no time). Any hints?
> 
> The speedup may not be noticeable if a lot of time is spent on
> evaluating the function. Would be interesting to profile.
> 
> The difference from before is that each time apply() is called, we
> only iterate over the actual facets included in your subdomain of the
> boundary, not the entire mesh and then skipping those facets which
> don't belong to your boundary. Also, depending on which type of search
> ("topological", "geometric", "pointwise"), the new implementation
> should avoid initializing mesh facets.
> 

Does this mean that there now is a distinct difference in performance
between giving the subdomain as a class that inherits from SubDomain
(overloading bool inside) and pre-computing a mesh function with
subdomain markers? /Dag