Exactly. Martin
On 30 January 2013 09:49, Johan Hake <[email protected]> wrote: > Very nice! > > So: > > f*dx > > will be assembled over all cells also if the mesh contains domain > information for some or all cells? > > Johan > > On 01/30/2013 09:32 AM, Martin Sandve Alnæs wrote: > > Hi all, > > yesterday I pushed a change to trunk, which fixes a long standing > > confusing issue. Unfortunately, the only way to stop this issue from > > confusing new users is to change the interpretation of some > > forms. Hopefully few codes will break from this change, but I'll explain > > it here so you can judge for yourself. > > > > Previously dx, ds and dS were aliases for dx(0), ds(0) and dS(0) > > respectively, and the assembler in dolfin interpreted a missing > > meshfunction for subdomains as if all cells were labeled with 0. So if > > you wrote a form > > u*v*dx [1a] > > or > > u*v*dx(0) [1b] > > and assembled it without specifying subdomains, you got the integral > > over the entire mesh in both cases. > > > > However if you wrote > > f*dx + g*dx(1) [2] > > and assembled it with subdomains, then f would only be integrated over > > the subdomain labeled 0, just as if you wrote > > f*dx(0) + g*dx(1) [3] > > This has naturally caused some confusion and bugs. > > > > With the development version of ufc,ufl,ffc,dolfin from today, you can > > explicitly write > > f*dx() + g*dx(1) [4] > > to integrate f over the entire domain and g over subdomain 1, > > independent of subdomain labeling. > > > > The breaking change is that [2] is now equivalent to [4], not [3]. > > > > That is, f*dx is now interpreted as f*dx(), and not as f*dx(0). This > > means that if you have code that depends on *dx being assembled only > > over subdomain 0, that code will break. I do not believe this to be a > > big problem, as it would be more natural to write explicitly dx(0) in > > such a case. However, if you do have such code, I recommend changing *dx > > to *dx(0) to be explicit, even if you are using 1.0 or 1.1 today. > > > > Martin > > > > > > _______________________________________________ > > Mailing list: https://launchpad.net/~fenics > > Post to : [email protected] > > Unsubscribe : https://launchpad.net/~fenics > > More help : https://help.launchpad.net/ListHelp > > > >
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