Anders Logg wrote:
> On Mon, Jun 23, 2008 at 08:03:35PM +0100, Garth N. Wells wrote:
>>
>> Anders Logg wrote:
>>> On Mon, Jun 23, 2008 at 07:31:09PM +0100, Garth N. Wells wrote:
>>>> Dag Lindbo wrote:
>>>>>> Anders Logg wrote:
>>>>>>> On Mon, Jun 23, 2008 at 02:51:05PM +0200, Dag Lindbo wrote:
>>>>>>>> Anders Logg wrote:
>>>>>>>>> On Thu, Jun 19, 2008 at 11:41:52PM +0200, Dag Lindbo wrote:
>>>>>>>>>> Hello again!
>>>>>>>>>>
>>>>>>>>>> Here comes another suggestion about the DOLFIN public interface:
>>>>>>>>>>
>>>>>>>>>> Constructing time dependent functions by subclassing from Function
>>>>>>>>>> and
>>>>>>>>>> TimeDependent is very very nice. The way u.sync(t) works by storing a
>>>>>>>>>> pointer to t is also very clever. However, I think it is too clever
>>>>>>>>>>
>>>>>>>>>> u.sync(&t)
>>>>>>>>>>
>>>>>>>>>> Today I misunderstood the reference nature of sync(t), and wrote code
>>>>>>>>>> like
>>>>>>>>>> this:
>>>>>>>>>>
>>>>>>>>>> while(t < T){
>>>>>>>>>> "compute timestep"
>>>>>>>>>> t += dt
>>>>>>>>>> sync_bc(t)
>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>> void sync_bc(real t){
>>>>>>>>>> for "all Dirichlet BCs"
>>>>>>>>>> bc.sync(t) // Pointer to stack memory gets assigned!!!!
>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>> :-( Of course, no one would be foolish enough to pass a pointer to
>>>>>>>>>> stack
>>>>>>>>>> memory knowingly in such a short lived context.
>>>>>>>>>>
>>>>>>>>>> /Dag
>>>>>>>>> TimeDependent does not seem to be used anywhere in the code so now
>>>>>>>>> it's just a fancy way of storing the current time. Objects that want
>>>>>>>>> to store the current time could equally well just add a member
>>>>>>>>>
>>>>>>>>> real t;
>>>>>>>>>
>>>>>>>>> I suggest we remove TimeDependent for now and add it back later when
>>>>>>>>> we find any use for it.
>>>>>>>>>
>>>>>>>>> ok?
>>>>>>>> No! It is really good feature for non-kernel applications.
>>>>>>>> I think there is a clear benefit for users to have this base class to
>>>>>>>> standardize things. It is one of only a handful situations where I
>>>>>>>> really like multiple inheritance!
>>>>>>>>
>>>>>>>> /Dag
>>>>>>> I understand, but since the interface is not used in DOLFIN, it's
>>>>>>> difficult to make any sense of how the class should behave.
>>>>>>>
>>>>>>> The current implementation is bound to cause trouble (as you have
>>>>>>> noticed) and I don't know how to fix it since I don't know how the
>>>>>>> class is used.
>>>>>>>
>>>>>> I think that the class is worth keeping and the simple change suggested
>>>>>> by Dag should remove the ambiguity.
>>>>>>
>>>>>> Garth
>>>>> I can make the (trivial) change and add a demo under
>>>>> function/TimeDependent/cpp
>>>>>
>>>> I just made the change, but please contribute a demo.
>>>>
>>>> Garth
>>> I'm not sure I like it but we can discuss it more later:
>>>
>>> 1. I think it should be a reference. The '&' signifies that we
>>> may access the address of the object just as much as '*'.
>>>
>> I'm rather indifferent. I like the look of 'real& t' (which is why I
>> originally did it that way), but accept that we generally pass scalars
>> by value throughout the code which may cause some confusion. Do you
>> suggest that we leave it as it was?
>
> No, I suggest we leave it like it is. I expect we will have some use
> for TimeDependent in the future, possibly in connection with the new
> TimeSeries class, and might want to make further modifications then.
>
BTW, it's currently used by two demos.
Garth
>
>
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