Dear Jonathan and Daniel,
Thank you for the quick responses. I've solved my problem. In my
method definition:
def setInitial(self):
self.a.setValue(linspace(1,7,self.nx))
self.b.setValue(1)
It is very important to call *.updateOld() after *.setValue().
Otherwise, the first sweep of the PDE will change the variable
drastically from the initial value.
As an aside, I really like the new toys in FiPy 3. Especially the
vector equation syntax.
Regards,
Lafras
On 4 December 2012 17:25, Jonathan Guyer <[email protected]> wrote:
>
> On Dec 4, 2012, at 10:08 AM, Daniel Wheeler wrote:
>
>> What I mean is: will all
>> variables be updated as they should be after each iteration of sweep &
>> updateOld?
>>
>> All "var.updateOld()" does is update the var's old value. Each CellVariable
>> (if "var.hasOld = True") has an "old" attribute, which is itself a
>> CellVariable. If the CellVariable has ("hasOld = False") then "var.old =
>> var". Now, the TransientTerm simply uses "(var - var.old) / dt". If there
>> are no sweeps then an old value is not required as "var" is implicit.
>> However, if your problem does have sweeps then you require an old value
>> otherwise "var.old" will be the value from the previous sweep rather than
>> the previous time step. Thus, if you use sweeps, you need to call
>> updateOld() on all your CellVariable's between each time step.
>
> While that's true, I'm not sure the updateOld() is particularly germane to
> Lafras' question. There's nothing special about being in __main__. If FiPy
> doesn't throw an error when you instantiate the variables, then there's no
> reason that any Variable expressions won't continue to work as you iterate
> the problem.
>
>
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