dolfin team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

On Saturday 27 February 2010 12:49:23 Garth N. Wells wrote:
> On Sat, 2010-02-27 at 19:58 +0100, Anders Logg wrote:
> > On Sat, Feb 27, 2010 at 06:32:12PM +0000, Garth N. Wells wrote:
> > > How do I pass the pointer to the first element of an array from the
> > > Python interface to a wrapped C++ function? I would like to tabulate
> > > the dofs of a cell, so I tried
> > >
> > >     local_facet = cell.index(facet)
> > >     dofs = numpy.array(9, dtype=numpy.uint32)
> > >     dof_map.tabulate_facet_dofs(dofs, local_facet)
> > >
> > > but I get a bunch of memory errors. I don't know to correctly allocate
> > > 'dofs' such that I can pass it to tabulate_facet_dofs.
> >
> > Try this:
> >
> >     cell_dofs = numpy.zeros(n, dtype='I')
> 
> Thanks. Did the trick.

An exception should have been raised here asking you to pass an array with 
dtype='I'.

Btw, I have never figured out the difference between the different uintXX in 
NumPy, versus the string descriptors.

Johan
 
> Garth
> 
> > It has worked for me before. Also note that there are dolfin::Cell
> > functions for some (but not all) of the functions in DofMap which
> > allows access from Python without needing to create a ufc::cell.
> >
> > --
> > Anders
> 
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