dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

I'm all for improved time support, but agree with Martin that a global
Time class is not the way to go.

Garth

On 15 February 2013 10:33, Johan Hake <hake.dev@xxxxxxxxx> wrote:
> I see your points. Introducing a Time handler class which is
> instantiated either by the user or by a solver might be the way to go.
> This, however becomes more tricky to integrate with the
> CompileExpression interface.
>
> However, one could include some magic to the code generation process so:
>
>   time = Time()
>   e = Expression("t", t=time)
>
> would generate an Expression with the shared time object attached to it,
> preferable as private member. With this I think there is no need for an
> explicit ExpressionWithTimeSupport class.
>
> Also if t is a scalar it would generate an ordinary Expression with a
> public double attribute.
>
> Johan
>
> On 02/15/2013 11:13 AM, Martin Sandve Alnæs wrote:
>> Of course if such a class ExpressionWithTimeSupport is generic and
>> useful enough and/or needed in official dolfin interfaces, the class can
>> be added to dolfin.
>>
>> Martin
>>
>>
>> On 15 February 2013 11:11, Martin Sandve Alnæs <martinal@xxxxxxxxx
>> <mailto:martinal@xxxxxxxxx>> wrote:
>>
>>     A single global time class is _not_ the way to go, that's not
>>     composable to multiphysics problems with different timescales, etc
>>     etc. It's a very narrow design for a very particular use case.
>>
>>     However this is designed, it's a necessity that the user creates the
>>     "time object" (whatever that is) and passes it to whatever parts of
>>     the code that should share the same view of the time.
>>
>>     The straightforward way to update time across Expression subclasses
>>     in C++ is to make the shared time a member of those classes.
>>
>>     class MyExpr: Expression {
>>       MyExpr(shared_ptr<Time> t)> t(t) {}
>>       void eval(...) { double now = t->get_time(); ... }
>>     }
>>
>>     This requires no library support. You can make a base class for
>>     Expressions with time support in your time solver code.
>>
>>     Martin
>>
>>
>
>
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