ufl team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Oct 21, 2008 at 05:41:15PM +0200, Martin Sandve Alnæs wrote:
> 2008/10/21 Anders Logg <logg@xxxxxxxxx>:
> > On Tue, Oct 21, 2008 at 05:27:55PM +0200, Anders Logg wrote:
> >> Is there a simple way to evaluate tensor expressions? For example, if
> >>
> >>  a = dot(v, u)*dx
> >>
> >> is there then a way to convert this to
> >>
> >>  v[0]*u[0] + v[1]*u[1] + ...
> >>
> >> ?
> >
> > I found the following in Dot:
> >
> >  def as_basic(self, dim, a, b):
> >      ii = Index()
> >      aa = a[ii] if (a.rank() == 1) else a[...,ii]
> >      bb = b[ii] if (b.rank() == 1) else b[ii,...]
> >      return aa*bb
> >
> > Why are the arguments dim, a and b required? A Dot already knows its
> > operands.
> >
> >> On Tue, Oct 21, 2008 at 05:27:55PM +0200, Anders Logg wrote:
> >> Is there a simple way to evaluate tensor expressions? For example, if
> >>
> >>  a = dot(v, u)*dx
> >>
> >> is there then a way to convert this to
> >>
> >>  v[0]*u[0] + v[1]*u[1] + ...
> >>
> >> ?
> >
> > I found the following in Dot:
> >
> >  def as_basic(self, dim, a, b):
> >      ii = Index()
> >      aa = a[ii] if (a.rank() == 1) else a[...,ii]
> >      bb = b[ii] if (b.rank() == 1) else b[ii,...]
> >      return aa*bb
> >
> > Why are the arguments dim, a and b required? A Dot already knows its
> > operands.
> >
> 
> Because it is used in an algorithm that first expands its operands,
> so a and b here are not necessarily its original operands.
> As you see, dim is not used here, but it's used in some other Compounds.
> 
> These functions could of course also be placed in the algorithm
> in question instead of in each Compound object, like with several
> other algorithms. But I think that's a detail we can discuss later,
> in context with other similar issues.

Yes, if as_basic does not work like a member function, it seems
strange to make it a member function. Maybe it could be made static if
necessary.

-- 
Anders

Attachment: signature.asc
Description: Digital signature