dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Nov 22, 2011 at 10:03:19PM +0000, Garth N. Wells wrote:
> On 22 November 2011 21:58, Anders Logg <logg@xxxxxxxxx> wrote:
> > On Tue, Nov 22, 2011 at 09:53:47PM +0000, Garth N. Wells wrote:
> >> On 22 November 2011 21:50, Anders Logg <logg@xxxxxxxxx> wrote:
> >> > On Tue, Nov 22, 2011 at 09:33:25PM +0000, Garth N. Wells wrote:
> >> >> On 22 November 2011 21:30, Anders Logg <logg@xxxxxxxxx> wrote:
> >> >> > On Tue, Nov 22, 2011 at 10:16:54PM +0100, Marie E. Rognes wrote:
> >> >> >> On 11/22/2011 09:55 PM, Anders Logg wrote:
> >> >> >> >On Tue, Nov 22, 2011 at 08:45:30PM +0000, Garth N. Wells wrote:
> >> >> >> >>
> >> >> >> >>On 21 Nov 2011, at 21:53, "Marie E. Rognes"<meg@xxxxxxxxx>  wrote:
> >> >> >> >>
> >> >> >> >>>
> >> >> >> >>>On 21. nov. 2011, at 21:52, Anders Logg<logg@xxxxxxxxx>  wrote:
> >> >> >> >>>
> >> >> >> >>>>On Mon, Nov 21, 2011 at 08:46:13PM +0000, Garth N. Wells wrote:
> >> >> >> >>>>>On 21 November 2011 13:07, Anders Logg<logg@xxxxxxxxx>  wrote:
> >> >> >> >>>>>>On Sun, Nov 20, 2011 at 11:55:43PM +0100, Anders Logg wrote:
> >> >> >> >>>>>>>On Sun, Nov 20, 2011 at 11:49:42PM +0100, Marie E. Rognes wrote:
> >> >> >> >>>>>>>>
> >> >> >> >>>>>>>>On 20. nov. 2011, at 23:31, Anders Logg<logg@xxxxxxxxx>  wrote:
> >> >> >> >>>>>>>>
> >> >> >> >>>>>>>>>Is anyone using the Function constructor that takes a vector as input
> >> >> >> >>>>>>>>>argument?
> >> >> >> >>>>>>>>>
> >> >> >> >>>>>>>>>Function u(V, x);
> >> >> >> >>>>>>>>>
> >> >> >> >>>>>>>>Yes.
> >> >> >> >>>>>>>Does it work? In parallel?
> >> >> >> >>>>>>>
> >> >> >> >>>>>>>Does it not work to instead use
> >> >> >> >>>>>>>
> >> >> >> >>>>>>>  x = u.vector()
> >> >> >> >>>>>>>
> >> >> >> >>>>>>>?
> >> >> >> >>>>>>>
> >> >> >> >>>>>>>If you need it, we should keep it but add an error message that it
> >> >> >> >>>>>>>doesn't work in parallel, unless it does...
> >> >> >> >>>>>>Any more input on this? There are several options:
> >> >> >> >>>>>>
> >> >> >> >>>>>>1. Remove this constructor
> >> >> >> >>>>>>
> >> >> >> >>>>>>2. Throw an error when running in parallel
> >> >> >> >>>>>>
> >> >> >> >>>>>>3. Check that the input vector makes sense
> >> >> >> >>>>>>
> >> >> >> >>>>>>The last one is problematic since I don't see an easy way to perform
> >> >> >> >>>>>>the check, other than calling get_local and having it fail.
> >> >> >> >>>>>>
> >> >> >> >>>>>I haven't heard any reason why it can't be removed. We may need to fix
> >> >> >> >>>>>assignment (re earlier discussion on assign) to just copy values and
> >> >> >> >>>>>not the whole object so that a user can get the vector and then assign
> >> >> >> >>>>>values to it without messing up the ghosting.
> >> >> >> >>>>Sounds good, but I want to wait for Marie to comment before I remove
> >> >> >> >>>>it. She is using it.
> >> >> >> >>>>
> >> >> >> >>>>Marie? Does it work for you to use x = u.vector()?
> >> >> >> >>>>
> >> >> >> >>>Probably. However removing the constructor would be changing parts of the basic interface, which I think is a bad idea.
> >> >> >> >>>
> >> >> >> >>>Add a warning if you want to deprecate it later.
> >> >> >> >>>
> >> >> >> >>Isn't the time to make an interface change now rather than later?
> >> >> >>
> >> >> >> I would say that the time to make an interface change before
> >> >> >> 1.0 has passed: I see more value in sticking to
> >> >> >> to what we have claimed, than in fixing this single instance.
> >> >> >>
> >> >> >> >True, but last time we discussed this was 1 hour or so before the
> >> >> >> >release of 1.0-rc1. Now we have a whole week to 1.0-rc2... :-)
> >> >> >> >
> >> >> >> >Marie, can you check again if that constructor is necessary?
> >> >> >>
> >> >> >> I'm typically using it for the same as the dolfin la/eigenvalue demo
> >> >> >> is using it for.
> >> >> >> Do you have a replacement syntax available?
> >> >
> >> > Marie, I think this should work:
> >> >
> >> >  u = Function(V)
> >> >  u.vector()[:] = x
> >> >
> >> > where x is the solution you get from the eigenvalue problem.
> >> >
> >> > Can you see if that works?
> >> >
> >>
> >> It won't,  because of a bad flaw in the vector assignment. It will
> >> make u.vector()[:] a copy of x (which has the wrong parallel layout) ,
> >> when what we want is to assign just the values.
> >
> > I thought you argued before that was the correct behavior? (When we
> > discussed the subfunction assignment last week.)
> >
>
> I argued that it is being done consistently, but not that it's right.
> We need to distinguish between copying and object and assigning just
> values of a vector (but not touching the layout, ghost values, etc) to
> another vector of the same length.

Agree.

> > Is it much work to fix that before 1.0-rc2?
> >
>
> Proper assignment is too much work. I'm adding a work-around fix now
> so the eigenvalue demo should be correct in parallel.

What are the implications for whether we should remove or keep that
constructor. We should only remove it if we can provide a working
alternative (assignment operator working).

--
Anders


> Garth
>
> >
> >
> >> Garth
> >>
> >> >
> >> >
> >> >
> >> >> >> That said, I'm not going to lose any sleep over this.
> >> >> >
> >> >> > Is everyone ok with throwing an error that it doesn't work in
> >> >> > parallel?
> >> >> >
> >> >>
> >> >> I don't think that is ideal.
> >> >>
> >> >> I building now with the constructors commented out to see how many
> >> >> changes would be required.
> >> >
> >> >
> >