The source of truth suggests Levi-Civita, alternating or permutation symbol: http://en.wikipedia.org/wiki/Levi-Civita_symbol
Mikael On 13 April 2011 20:31, Martin Sandve Alnæs <marti...@simula.no> wrote: > That should be fairly easy to do, can be handled similarly to Identity. > > I = Identity(cell.d) > f = I[i,j] * ... > > e = Permutation(cell.d) > f = e[i,j,l] * v[j]*w[i]*v[l]*dx > > Other suggestions for naming? > > Martin > > On 13 April 2011 20:24, Garth N. Wells <gn...@cam.ac.uk> wrote: > >> The permutation symbol should be added to UFL. >> >> Garth >> >> On 13/04/11 19:20, Martin Sandve Alnæs wrote: >> > Python does not know anything about implicit index summation, so in your >> > code e() is only called once, and reaches the else condition and thus >> > returns 0.0. >> > >> > Similar to as_vector, you can use the as_tensor function, since you need >> > three dimensions. >> > >> > Martin >> > >> > On 13 April 2011 19:04, B. Emek Abali >> > <question152...@answers.launchpad.net >> > <mailto:question152...@answers.launchpad.net>> wrote: >> > >> > New question #152702 on DOLFIN: >> > https://answers.launchpad.net/dolfin/+question/152702 >> > >> > May be a non-needed trial for some, but I try to define an >> > expression (permutation symbol) >> > >> > def e(i,j,k): >> > if (i,j,k) == (1.0,2.0,3.0): return 1.0 >> > elif (i,j,k) == (2.0,3.0,1.0): return 1.0 >> > elif (i,j,k) == (3.0,1.0,2.0): return 1.0 >> > elif (i,j,k) == (3.0,2.0,1.0): return -1.0 >> > elif (i,j,k) == (2.0,1.0,3.0): return -1.0 >> > elif (i,j,k) == (1.0,3.0,2.0): return -1.0 >> > else: return 0.0 >> > >> > and use (with summation over indices, it is a curl operator >> > contracted with w) in the form like >> > >> > f=v[j]*w[i]*e(i,j,l)*v[l]*dx >> > >> > which raises: >> > ufl.log.UFLException: Trying to integrate expression of rank 0 with >> > free indices >> > >> > Do I have to use as_vector(...) type definition to sum with indices >> > or is there a nice possibility to let it sum over the arguments of >> > e(...) expression? >> > >> > -- >> > You received this question notification because you are a member of >> > DOLFIN Team, which is an answer contact for DOLFIN. >> > >> > _______________________________________________ >> > Mailing list: https://launchpad.net/~dolfin >> > Post to : dolfin@lists.launchpad.net >> > <mailto:dolfin@lists.launchpad.net> >> > Unsubscribe : https://launchpad.net/~dolfin >> > More help : https://help.launchpad.net/ListHelp >> > >> > >> > >> > >> > _______________________________________________ >> > Mailing list: https://launchpad.net/~dolfin >> > Post to : dolfin@lists.launchpad.net >> > Unsubscribe : https://launchpad.net/~dolfin >> > More help : https://help.launchpad.net/ListHelp >> >> _______________________________________________ >> Mailing list: https://launchpad.net/~dolfin >> Post to : dolfin@lists.launchpad.net >> Unsubscribe : https://launchpad.net/~dolfin >> More help : https://help.launchpad.net/ListHelp >> > > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : dolfin@lists.launchpad.net > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp > >
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