ufl team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

On Saturday 23 January 2010 08:36:34 Garth N. Wells wrote:
> Anders Logg wrote:
> > On Sat, Jan 23, 2010 at 10:35:03AM +0000, Garth N. Wells wrote:
> >> I've run into an issue when using 'exp' on a Coefficient/Function. In a
> >> .ufl file, I can use
> >>
> >>   M = exp(T)
> >>
> >> where T is a Coefficient without problems. Using PyDOLFIN, I get the
> >> error:
> >>
> >>   AttributeError: exp
> >>
> >> Could this be that the Python version of exp is being called, rather
> >> than the UFL version? How can I check in Python which 'exp' function is
> >> being called?
> >>
> >> Garth
> >
> > print should work. With UFL, I expect you would get something like
> >
> > # print exp
> > <function exp at 0x2673aa0>
> 
> This is what I get when running ffc on a .ufl file and it works.
> 
> > Otherwise something like
> >
> > # print exp
> > <ufunc 'exp'>
> 
> This is what I get from PyDOLFIN and it breaks. Is this likely to be
> what causes my problem? Any ideas on how to fix it?

You can remove the last line in dolfin/__init__.py:

  from numpy import sin, cos, exp

I suppose these are exposed to the dolfin interface so they can be used when 
sub classing Expression in Python. However with ufl and the mature compile 
function interface I think these functions should be removed. 

If they are used in any demo, one can import them from the correct module, 
which should be math instead of numpy (as the usage is not vectorized), either 
as:

  from math import exp as mexp
  ...
     def eval(self, values, x):
         values[0] = mexp(x[0])

or just:

  import math
  ...
     def eval(self, values, x):
         values[0] = math.exp(x[0])

Johan

> Garth
> 
> 
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