dolfin team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

On Tuesday November 30 2010 14:48:09 Garth N. Wells wrote:
> On 30/11/10 22:37, Johan Hake wrote:
> > On Tuesday November 30 2010 14:30:18 Garth N. Wells wrote:
> >> On 30/11/10 22:25, Anders Logg wrote:
> >>> On Tue, Nov 30, 2010 at 10:20:52PM +0000, Garth N. Wells wrote:
> >>>> We have a thread-safe problem in GenericFunction with the member
> >>>> object
> >>>> 
> >>>>     mutable Data data;
> >>>> 
> >>>> Any ideas on how to get rid of it? We really should pass data
> >>>> through the function interfaces, but we're constrained in this case
> >>>> by the UFC interface.
> > 
> > This is ironical, as Data was introduced so we in the future (now
> > present) could be thread safe...
> 
> Really? I remember Martin always warning against such a design because
> it's not thread-safe.

We went from keeping a Cell member (and what not) to pass all data through the 
Data object in the eval method. Hoever, when GenericFunction become a subclass 
of ufc::function a Data member sneaked in and, we are back where we started ;)

> > But I do not think GenericFunction was a ufc::function
> > at that time.
> > 
> > Is it time to introduce the notion of thread in the ufc interface?
> 
> Not for this purpose. What would be helpful is a way to pass
> user-defined data through the UFC interface. Perhaps more importantly,
> we should avoid using 'mutable'. A 'const' object should in principle be
> thread-safe, but using mutable clouds this.

Ok.

Johan

> Garth
> 
> > Johan
> > 
> >>> Is it possible to have a pool of Data objects and have each thread
> >>> 
> >>> select the proper one:
> >>>     data[thread_id]
> >> 
> >> That's messy because the Data object is buried deep in the code.
> >> 
> >> I think that we should avoid this design (private scratch space) and try
> >> to figure out an alternative. I removed the private scratch from
> >> Function the other day.
> >> 
> >>> --
> >>> Anders
> >> 
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