dolfin team mailing list archive

["Martin Sandve Alnæs" <martinal@xxxxxxxxx>]

2008/12/6 Johan Hake <hake@xxxxxxxxx>:
> On Saturday 06 December 2008 15:37:15 Martin Sandve Alnæs wrote:
>> 2008/12/6 Johan Hake <hake@xxxxxxxxx>:
>> > On Saturday 06 December 2008 14:48:34 Anders Logg wrote:
>> >> On Sat, Dec 06, 2008 at 02:41:55PM +0100, Johan Hake wrote:
>> >> > On Saturday 06 December 2008 14:23:40 Anders Logg wrote:
>> >> > > On Sat, Dec 06, 2008 at 12:02:43PM +0100, Johan Hake wrote:
>> >> > > > On Friday 05 December 2008 18:02:07 Anders Logg wrote:
>> >> > > > > I'm having problems getting vector-valued constants working.
>> >> > > > > Take a look at
>> >> > > > >
>> >> > > > >     demo/pde/stokes/taylor-hood/python
>> >> > > > >
>> >> > > > > It reports
>> >> > > > >
>> >> > > > >     assert(isinstance(defaults[i], (dict,
>> >> > > > > types.NoneType)),"Wrong type in 'defaults'")
>> >> > > > >    TypeError: 'NoneType' object is unsubscriptable
>> >> > > > >
>> >> > > > > It seems like defaults is set to None and then defaults is
>> >> > > > > indexed.
>> >> > > > >
>> >> > > > > Any ideas?
>> >> > > >
>> >> > > > Should be fixed now. I have added better argument checking to
>> >> > > > compile_function. But you have to send in a tuple of strings to
>> >> > > > compile_function if you want to produce a vector values function.
>> >> > > > A list is interpreted as len(cppexpr) number of scalar functions.
>> >> > > >
>> >> > > > This is a bit fragile, but it is documented in the Function doc
>> >> > > > string.
>> >> > >
>> >> > > ok! I wasn't aware of the difference.
>> >> > >
>> >> > > Maybe we should have both compile_function and compile_functions
>> >> > > instead of differentiating between tuples and lists?
>> >> > >
>> >> > > There is already a compile_functions defined in
>> >> > > compile_functions.py, but that does not seem to be used. Should it
>> >> > > be removed (and the name reused for batch-processing functions)?
>> >> >
>> >> > compile_functions.py is the orginal work of Martin. It is depricated
>> >> > now.
>> >> >
>> >> > The compile_function module should not be exposed to the user, (Martin
>> >> > might have a different opinion here) so it should be sufficient with
>> >> > the Function interface.
>> >> >
>> >> > The differences between compiling one and several functions are so
>> >> > small that I do not think it is usefull to split the code into
>> >> > different modules.
>> >> >
>> >> > One could use the name Functions, instead of Function for batch
>> >> > processing. In this way we make clear for a user what it means. This
>> >> > also correlates with the TestFunction/TestFunctions.
>> >> >
>> >> > Unfortunaltly will not the case of defining several functions in a
>> >> > cppcode, argument be covered by this, as the number of compiled
>> >> > functions will depend on how many functions the user defines in the
>> >> > cppcode. For this case we could add CostumFunctions, or something.
>> >> >
>> >> > Or just keep it the way it is with clearer documentation?
>> >>
>> >> Wouldn't it be easy to add an additional argument batch=False to
>> >> compile_function? Then you could check that argument instead of
>> >> differentiating between lists and tuples.
>> >
>> > So,
>> >
>> >  f = Function(V,cppexpr = (("sin(x[0])","cos(x[1])"),
>> >                           (("sin(x[1])","exp(x[1])"))))
>> >
>> > would create a tensor valued function and:
>> >
>> >  f, g = Function(V,cppexpr = (("sin(x[0])","cos(x[1])"),
>> >                              (("sin(x[1])","exp(x[1])")),
>> >                               batch = True)
>> >
>> > would create two vector valued functions. Then we need to explain that
>> > the use of batch = True, change the meaning of the outermost parentesis
>> > from a matrix expression to a list expression of two vectors. I have bad
>> > feeling...
>> >
>> > We could also be a bit radical and adapt a pylab.plot interface to the
>> > compile_function module
>> >
>> >  f, c = FunctionExpression(V0,("sin(x[0])","cos(x[1])"),V1,"2.5")
>> >
>> > where a space followed by an expression will associate the space with
>> > that expression. We can have an optional number of (V, cppexpr)
>> > combinations. And the natural extension of:
>> >
>> >  f0, f1, f2  = FunctionExpression("sin(x[0])","cos(x[1])","2.5", space =
>> > V)
>> >
>> > where each compiled function is instantiated with the function space
>> > defined in 'space'. This could be followed up with e.g:
>> >
>> >  CostumFunction(V0,code0,V1,code1)
>> >
>> > and
>> >
>> >  CostumFunction(code0,code1, space = V)
>> >
>> > (The names may not be the best...)
>> >
>> > Johan
>>
>> I like
>>
>> f0, f1, f2 = Functions(V0, code0, V1, code1, V2, code2)
>>
>> e.g.
>>
>> f0, f1, f2 = Functions(V0, "sin(x[0])",
>>                                  V1, ("cos(x[0])", "sin(x[1])"),
>>                                  V2, (("a", "b"), ("c", "d")))
>
> Maybee the best? The probelm here is to distinct between code and a scalar
> expression. Maybee a simple
>
>  if "class" in arg:
>    compilecode
>  else:
>    compile_expression

We'll need to use a regexp to get the class name for construction.
I think there is some code like that in compile_functions?

> If this is what we want I rather go for just
>
>  Function(...)
>
> The analogy to pylab.plot would be that it is named plot not plots.

The big difference is that plot is a verb and function is a noun.
plot(a,b,c) can be read "plot these three things" while
f, g, h = Function(a,b,c) has no such natural language interpretation.

In fact, I'd like to use "functions" instead, with lower case.

>> (we will remove Functions from UFL, so I guess the naming is ok after all).
>>
>> Have you kept the automatic variable construction? The code above would
>> make a, b, c, d double variables of f2:
>>   f2.a = 1.23
>
> Yup, together with a 'defaults' argument. This could be added in the above
> syntax as:
>
>   f0, f1, f2 = Function(V0, "sin(x[0])",
>                         V1, ("cos(x[0])", "sin(x[1])"),
>                         V2, (("a", "b"), ("c", "d")),{"a":1.0,"b":2.0})
>
> These are then optional, but directly tied to the previous expression.

Nice.

-- 
Martin