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)
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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