On Tuesday April 26 2011 08:48:33 Garth N. Wells wrote:
> On 26/04/11 16:44, Johan Hake wrote:
> > On Tuesday April 26 2011 08:42:32 Anders Logg wrote:
> >> On Tue, Apr 26, 2011 at 08:39:30AM -0700, Johan Hake wrote:
> >>> On Tuesday April 26 2011 08:33:11 Garth N. Wells wrote:
> >>>> On 26/04/11 16:31, Johan Hake wrote:
> >>>>> On Tuesday April 26 2011 08:16:29 Garth N. Wells wrote:
> >>>>>> On 26/04/11 16:07, Anders Logg wrote:
> >>>>>>> On Tue, Apr 26, 2011 at 03:59:52PM +0100, Garth N. Wells wrote:
> >>>>>>>> On 26/04/11 15:55, Anders Logg wrote:
> >>>>>>>>> On Tue, Apr 26, 2011 at 03:45:22PM +0100, Garth N. Wells wrote:
> >>>>>>>>>> On 26/04/11 13:51, Anders Logg wrote:
> >>>>>>>>>>> On Tue, Apr 26, 2011 at 02:00:50PM +0200, Anders Logg wrote:
> >>>>>>>>>>>> It feels good that you trust me enough to handle it. ;-)
> >>>>>>>>>>>>
> >>>>>>>>>>>> Will add it sometime this afternoon and then we can revisit
> >>>>>>>>>>>> the JIT compiler caching.
> >>>>>>>>>>>
> >>>>>>>>>>> I'm getting confused here... Looking at preprocess.py in UFL, I
> >>>>>>>>>>> see
> >>>>>
> >>>>> this:
> >>>>>>>>>> It is confusing. Does the function 'preprocess' do anything that
> >>>>>>>>>> the old FormData class didn't? It would be easier to follow if
> >>>>>>>>>> Form just had a member function form_data() that computes and
> >>>>>>>>>> stores data (like it used to), or if Form had a 'preprocess'
> >>>>>>>>>> function. Having the function preprocess return a new form is
> >>>>>>>>>> really confusing.
> >>>>>>>>>
> >>>>>>>>> I don't find that particularly confusing. It's the same as
> >>>>>>>>>
> >>>>>>>>> refined_mesh = refine(mesh)
> >>>>>>>>
> >>>>>>>> Which is the whole problem. By creating a new object, FormData is
> >>>>>>>> thrown away. The preprocessing should just compute some more data,
> >>>>>>>> just like we *don't* do
> >>>>>>>>
> >>>>>>>> initialised_mesh = mesh.init(0)
> >>>>>>>>
> >>>>>>>> What was wrong with Martin's original design that necessitated the
> >>>>>>>> change?
> >>>>>>>
> >>>>>>> As I explained, I thought it was better to have an explicit call to
> >>>>>>> preprocess since that makes it clear that one makes a call to a
> >>>>>>> function which may take some time to execute (instead of just
> >>>>>>> calling a member function which seems to just return some data).
> >>>>>>>
> >>>>>>> But as I say above: I added the caching back at some point (maybe
> >>>>>>> even the day after I removed it 2 years ago) so we don't need to
> >>>>>>> discuss why I removed it (as I realized myself I shouldn't have
> >>>>>>> removed it and added it back a long time ago).
> >>>>>>>
> >>>>>>> What has me confused now is that the caching seems to be in place
> >>>>>>> but we still need the extra caching in FFC/DOLFIN and I don't see
> >>>>>>> why.
> >>>>>>
> >>>>>> Because preprocess returns a new form, e.g. define a form
> >>>>>>
> >>>>>> a = u*v*dx
> >>>>>> jit(a)
> >>>>>>
> >>>>>> Inside jit,
> >>>>>>
> >>>>>> a.form_data() is None:
> >>>>>> b = preprocess(a) # b now has data attached, but a doesn't
> >>>>>>
> >>>>>> else:
> >>>>>> b = a
> >>>>>>
> >>>>>> Now 'b' has been preprocessed, and has form data attached, but 'a'
> >>>>>> doesn't. Calling 'jit(a)' again, the code will never enter the
> >>>>>> 'else' part of the clause because 'a' never gets any form data.
> >>>>>> Johan has added some code FFC that attaches the form data of 'b' to
> >>>>>> 'a', but it is a bit clumsy.
> >>>>>
> >>>>> No, it was already attached. I just made ffc use it.
> >>>>
> >>>> Didn't you add the line
> >>>>
> >>>> form._form_data = preprocessed_form.form_data()
> >>>
> >>> No, I added:
> >>> preprocessed_form = form.form_data()._form
> >>>
> >>> I think the thing here is that form_data has always had a preprocessed
> >>> form. Someone (lets not point fingers!) thought that was too much magic
> >>> and added an
> >>>
> >>> explicit need to call:
> >>> form = preprocess(form)
> >>>
> >>> in jit_compiler(). This made the design more complicated and also
> >>> introduced a cirucular dependency, as the return preprocessed form need
> >>> to know of its form_data, but the form_data already had a reference to
> >>> the preprocessed form. The latter is what I used in the one line I
> >>> altered.
> >>
> >> No, it made the design cleaner since it makes clear something needs to
> >> happen to get the metadata: a call to preprocess.
Why is:
form_data = form.form_data()
preprocessed_form = form_data._form
so bad?
> How about something like
>
> a.compute_form_data()
>
> to compute the data, and
>
> data = a.form_data()
>
> to get the FormData. This is like Martin's orginal design, except
> form_data() returns None if the data hasn't been computed.
I think this adds more to the form than is nessesary.
Johan
> Garth
>
> >> Where did you add this line?
> >
> > I change
> >
> > preprocessed_form = form
> >
> > to:
> > preprocessed_form = form.form_data()._form
> >
> > Johan
> >
> >> --
> >> Anders
> >>
> >>> Johan
> >>>
> >>>> ?
> >>>>
> >>>> Garth
> >>>>
> >>>>>> Better would be
> >>>>>>
> >>>>>> a.preprocess()
> >>>>>>
> >>>>>> or
> >>>>>>
> >>>>>> a.form_data()
> >>>>>
> >>>>> As already mentioned in a previous email, I suggest we only call
> >>>>> form_data(). This will return the form_data. The preprocessed form is
> >>>>> attached to the form_data and this is what is passed to the code
> >>>>> generator. I am pretty sure this is what was there from the
> >>>>> beginning.
> >>>>>
> >>>>> It is confusing to call:
> >>>>> form = preprocess(form)
> >>>>>
> >>>>> as the preprocessed form was never ment to be doing anything but
> >>>>> being passed to the code generator, AFAIK.
> >>>>>
> >>>>> Johan
> >>>>>
> >>>>>> Garth
> >>>>>>
> >>>>>>>> Garth
> >>>>>>>>
> >>>>>>>>>> Garth
> >>>>>>>>>>
> >>>>>>>>>>> def preprocess(form, object_names={}, common_cell=None):
> >>>>>>>>>>> ...
> >>>>>>>>>>>
> >>>>>>>>>>> # Check that form is not already preprocessed
> >>>>>>>>>>>
> >>>>>>>>>>> if form.form_data() is not None:
> >>>>>>>>>>> debug("Form is already preprocessed. Not updating form
> >>>>>>>>>>> data.") return form
> >>>>>>>>>>>
> >>>>>>>>>>> ...
> >>>>>>>>>>>
> >>>>>>>>>>> # Attach form data to form
> >>>>>>>>>>> form._form_data = form_data
> >>>>>>>>>>>
> >>>>>>>>>>> # Attach preprocessed form to form data
> >>>>>>>>>>> form_data._form = form
> >>>>>>>>>>>
> >>>>>>>>>>> And when I look at the blamelist (bzr annotate), it looks like
> >>>>>>>>>>> I added those lines, so I must have come to my senses and
> >>>>>>>>>>> added it back at some point (way back). So in conclusion,
> >>>>>>>>>>> calling preprocess() should not taking any time.
> >>>>>>>>>>>
> >>>>>>>>>>> What am I missing?
> >>>>>>
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