Martin Sandve Alnæs wrote:
2008/7/2 Dag Lindbo <dag@xxxxxxxxxx>:
Martin Sandve Alnæs wrote:
I just added checks for valid Functions to the assembler, but this
turned out to break some demos so I changed it to warnings.
This seems like helpful checks to make!
The reason is that Function(mesh, 0.0), which creates a ConstantFunction,
is used for zero vector functions as well, which leaves the value shape
of such a function undefined. This makes error checking impossible,
which is not very nice.
In my opinion, the correct next step is to keep these warnings,
and turn them into errors after "a while". We should either add
support for ConstantFunctions with tensor shape (would be nice),
or make the demos and apps use user-define functions.
Adding tensor shape to the existing concept of ConstantFunction seems
like the way to go. IMHO, the convenience if this over user defined
functions is too great to discard.
Would it not just amount to having ConstantFunction::rank() return the
proper value as determined by the mutable member size, instead of 0? (on
line 28 of ConstantFunction.cpp)
No, because this size isn't known at construction time, only when
interpolate is called with a finite_element object. A suitable (set
of) constructor(s) needs to be defined, mirrored in Function, and
handled in the swig interface for python.
Yes, I see that this is needed if the rank and shape of the function is
to be set constructor. Clearly, this makes for a nice user interface! My
suggestion was more along the lines of a quick fix to get rid of the
warnings: rank() returns zero if size == 1, returns 1 if size == 2 or 3 etc.
/Dag
// Scalar constructor
Function f(mesh, 0.0);
// General tensor constructor:
Function f(Mesh& mesh, uint rank, uint* shape, uint* values);
// vector
uint rank = 1;
uint shape[1] = { 2 };
real values[2] = { 1., 2. };
Function f(mesh, rank, shape, values);
// or
uint size = 2;
real values[2] = { 1., 2. };
Function f(mesh, 1, &size, values);
// 3x3 tensor:
uint rank = 2;
uint shape[2] = { 3, 3 };
real values[9] = {
1., 2., 3.,
4., 5., 6.,
7., 8., 9. };
Function f(mesh, rank, shape, values);
