Garth N. Wells wrote:
>
> Anders Logg wrote:
>> On Wed, Mar 11, 2009 at 11:15:44PM +0100, Anders Logg wrote:
>>> On Wed, Mar 11, 2009 at 11:01:56PM +0100, DOLFIN wrote:
>>>> One or more new changesets pushed to the primary dolfin repository.
>>>> A short summary of the last three changesets is included below.
>>>>
>>>> changeset: 5853:f1ef6132a568d5a56e5c70b17ce118c19bfa961c
>>>> tag: tip
>>>> user: Anders Logg <[email protected]>
>>>> date: Wed Mar 11 23:01:49 2009 +0100
>>>> files: ChangeLog demo/pde/poisson/cpp/Poisson.h
>>>> dolfin/function/Function.cpp sandbox/misc/Poisson.form
>>>> sandbox/misc/Poisson.h sandbox/misc/README sandbox/misc/SConstruct
>>>> sandbox/misc/cpp/Poisson.form sandbox/misc/cpp/Poisson.h
>>>> sandbox/misc/cpp/SConstruct sandbox/misc/cpp/main.cpp sandbox/misc/main.cpp
>>>> description:
>>>> Automatically interpolate user-defined functions on assignment
>>> This is something we discussed a while back but we didn't agree on
>>> whether or not it was a good idea. I think it is and it's easy enough
>>> to remove if there is strong enough pressure against it.
>>>
>>> Here are two examples of assignment:
>>>
>>> Case 1: Time-stepping with user-defined initial data
>>>
>>> # Initializations
>>> mesh = UnitSquare(32, 32)
>>> V = FunctionSpace(mesh, "Lagrange", 1)
>>> u0 = Function(V, "sin(x[0])")
>>> u1 = Function(V)
>>>
>>> # Time stepping
>>> for i in range(10):
>>>
>>> print i
>>>
>>> # Solve for u1
>>> u1.vector()
>>>
>>> # Assign u0 = u1
>>> u0.assign(u1)
>>>
>>>
>>> This works fine since u1 is defined by a vector of dofs so the
>>> assignment is allowed.
>>>
>>> Case 2: Time-stepping with user-defined coefficient
>>>
>>> # Initializations
>>> mesh = UnitSquare(32, 32)
>>> V = FunctionSpace(mesh, "Lagrange", 1)
>>> w0 = Function(V)
>>> w1 = Function(V, "sin(t*x[0])")
>>>
>>> # Time stepping
>>> for i in range(10):
>>>
>>> print i
>>>
>>> # Update w1
>>> w1.t = float(i)
>>>
>>> # Solve for u
>>>
>>> # Assign w0 = w1 (does not work)
>>> w0.assign(w1)
>>> #w0 = interpolate(w1, V)
>>> #w0 = project(w1, V)
>>>
>>> This breaks since assignment is not allowed from the user-defined
>>> Function w1. Interpolation or projection helps, but each of these
>>> return a new function, which will confuse the JIT compiler (at least
>>> the current FFC JIT compiler) and lead to excessive generation of code
>>> (no cache reuse).
>>>
>>> The new version of the assignment operator allows this kind of
>>> assignment and automatically interpolates when necessary. It also
>>> prints out the following message:
>>>
>>> Assignment from user-defined function, interpolating.
>>>
>>> So it should be clear what happens. Any objections?
>> Any more thoughts on this?
>>
>
> Below is how I would prefer to have it:
>
> Case 1: Time-stepping with user-defined initial data
>
> # Initializations
> mesh = UnitSquare(32, 32)
> V = FunctionSpace(mesh, "Lagrange", 1)
> u0 = Function(V, "sin(x[0])")
> u1 = Function(V)
>
> # Interpolate the initial data
> u0.interpolate()
>
> # Time stepping
> for i in range(10):
>
> print i
>
> # Solve for u1
> u1.vector()
>
> # Assign u0 = u1
> u0.assign(u1)
>
I've changed my mind for the above example. If u0 is defined as
u0 = Function(V, "sin(x[0])")
(it has a FunctionSpace) then interpolation upon assignment is OK. What
I would object to is a user-defined Function which does not yet have a
FunctionSpace being interpolated (which might be prevented by the
current design anyway).
Garth
> We now have interpolation upon assignment, but why not for example
> projection upon assignment? Either way the Function being assigned to is
> not the same as the Function on the RHS of the assignment operator.
>
> Garth
>
>>
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