July 2016 - firedrake - imperial.ac.uk

Re: [firedrake] Using Firedrake to model optical fibres
by David Ham 05 Jul '16

05 Jul '16

Hi Ian, Thanks for your interest in Firedrake. You could definitely solve Maxwell's equations in real space in Firedrake, even using the right exterior calculus discrete function spaces. It will also work in parallel for free. I'm less sure whether we can do Fourier space. I think I'd need to see the formulation. In particular, we can't currently solve PDEs over the complex numbers - although there are some work arounds for this. (Complex is definitely on the wish list but it will only happen if I manage to attract the right masters student to work on it). Regards, David On Tue, 5 Jul 2016 at 14:35 Ian Thompson <I.R.Thompson(a)bath.ac.uk> wrote: > Hello all, > > I saw Firedrake at the Bath HPC day, I work in physics and we do a lot of > fibre optic research. This includes modelling Maxwell’s equations across a > 2D mesh that describes a cross-section of a fibre. Traditionally we solve > this using a finite element method and solving in Fourier space. Is > Firedrake suitable for solving such problems? > Looking at the documentation Firedrake can load meshes from other > programs, to solve in Fourier space would it be sufficient to define the > equations in Fourier space and load a mesh that corresponds to the Fourier > transform of our real space structure. Or can Firedrake support the > transform itself? Would Firedrake be capable of solving the equations in > real-space? In principle there is no problem with solving in real-space, > its just been neater in the past. > Currently we use COMSOL which is expensive and slow due to a lot of > unnecessary (for our purposes at least) overhead and lack of parallel > licensing. Sorry for so many questions but I am quietly excited at using a > neater, nicer solver. > > Cheers > Ian > _______________________________________________ > firedrake mailing list > firedrake(a)imperial.ac.uk > https://mailman.ic.ac.uk/mailman/listinfo/firedrake >

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Using Firedrake to model optical fibres
by Ian Thompson 05 Jul '16

05 Jul '16

Hello all, I saw Firedrake at the Bath HPC day, I work in physics and we do a lot of fibre optic research. This includes modelling Maxwell’s equations across a 2D mesh that describes a cross-section of a fibre. Traditionally we solve this using a finite element method and solving in Fourier space. Is Firedrake suitable for solving such problems? Looking at the documentation Firedrake can load meshes from other programs, to solve in Fourier space would it be sufficient to define the equations in Fourier space and load a mesh that corresponds to the Fourier transform of our real space structure. Or can Firedrake support the transform itself? Would Firedrake be capable of solving the equations in real-space? In principle there is no problem with solving in real-space, its just been neater in the past. Currently we use COMSOL which is expensive and slow due to a lot of unnecessary (for our purposes at least) overhead and lack of parallel licensing. Sorry for so many questions but I am quietly excited at using a neater, nicer solver. Cheers Ian

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Re: [firedrake] making a broken element from a Function Space
by Colin Cotter 05 Jul '16

05 Jul '16

OK, this seems to work. I made a PR in FIAT. cheers --cjc On 5 July 2016 at 11:01, Cotter, Colin J <colin.cotter(a)imperial.ac.uk> wrote: > Ah, I assumed it was being tested in the hybridisation test but then I > remembered that one doesn't do extruded elements. > > cheers > --cjc > > On 5 July 2016 at 10:27, Mitchell, Lawrence < > lawrence.mitchell(a)imperial.ac.uk> wrote: > >> >> > On 5 Jul 2016, at 10:20, Colin Cotter <colin.cotter(a)imperial.ac.uk> >> wrote: >> > >> > Yes, it then just hit another use of ref_el lower down. I can fix this >> of course, but I wonder if I am doing something weird since this is just >> the usual usage of BrokenElement and hasn't been an issue in other examples. >> >> >> They're not used in any tests on extruded elements. Which is probably >> why this issue hasn't appeared. >> >> Lawrence >> > > > > -- > http://www.imperial.ac.uk/people/colin.cotter > > www.cambridge.org/9781107663916 > > > -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916

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Re: [firedrake] making a broken element from a Function Space
by Colin Cotter 05 Jul '16

05 Jul '16

Ah, I assumed it was being tested in the hybridisation test but then I remembered that one doesn't do extruded elements. cheers --cjc On 5 July 2016 at 10:27, Mitchell, Lawrence < lawrence.mitchell(a)imperial.ac.uk> wrote: > > > On 5 Jul 2016, at 10:20, Colin Cotter <colin.cotter(a)imperial.ac.uk> > wrote: > > > > Yes, it then just hit another use of ref_el lower down. I can fix this > of course, but I wonder if I am doing something weird since this is just > the usual usage of BrokenElement and hasn't been an issue in other examples. > > > They're not used in any tests on extruded elements. Which is probably why > this issue hasn't appeared. > > Lawrence > -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916

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Re: [firedrake] making a broken element from a Function Space
by Colin Cotter 05 Jul '16

05 Jul '16

Yes, it then just hit another use of ref_el lower down. I can fix this of course, but I wonder if I am doing something weird since this is just the usual usage of BrokenElement and hasn't been an issue in other examples. --cjc On 5 July 2016 at 10:00, Mitchell, Lawrence < lawrence.mitchell(a)imperial.ac.uk> wrote: > > > On 5 Jul 2016, at 09:41, Colin Cotter <colin.cotter(a)imperial.ac.uk> > wrote: > > > > Actually, I'm now less sure where the problem is. > > > > If I do this, in the state object > > ... > > self.V_elt[2] = V2t_elt > > ... > > > > and then later, > > Vtdg_elt = BrokenElement(state.V_elt[2]) > > Vtdg = FunctionSpace(mesh, Vtdg_elt) > > > > then I get the same error. > > Did you try my suggestion? > > Lawrence > -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916

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Re: [firedrake] making a broken element from a Function Space
by Colin Cotter 05 Jul '16

05 Jul '16

Actually, I'm now less sure where the problem is. If I do this, in the state object ... self.V_elt[2] = V2t_elt ... and then later, Vtdg_elt = BrokenElement(state.V_elt[2]) Vtdg = FunctionSpace(mesh, Vtdg_elt) then I get the same error. --cjc On 5 July 2016 at 09:31, Mitchell, Lawrence < lawrence.mitchell(a)imperial.ac.uk> wrote: > > > On 5 Jul 2016, at 09:23, Colin Cotter <colin.cotter(a)imperial.ac.uk> > wrote: > > > > Dear Firedrakers, > > I have a bit of code where I want to construct a broken function space > corresponding to a given function space. > > > > My code is: > > Vdg_elt = BrokenElement(V.ufl_element()) > > Vdg = FunctionSpace(state.mesh, Vdg_elt) > > > > This returns an error: > > File "/home/cjc1/repositories/dcore/gusto/advection.py", line 199, in > __init__ > > Vdg = FunctionSpace(state.mesh, Vdg_elt) > > File "<decorator-gen-291>", line 2, in FunctionSpace > > File "/home/cjc1/firedrake/src/PyOP2/pyop2/profiling.py", line 59, in > wrapper > > return f(*args, **kwargs) > > File "/home/cjc1/firedrake/src/firedrake/firedrake/functionspace.py", > line 131, in FunctionSpace > > new = impl.FunctionSpace(topology, element, name=name) > > File > "/home/cjc1/firedrake/src/firedrake/firedrake/functionspaceimpl.py", line > 245, in __init__ > > sdata = get_shared_data(mesh, fiat_element) > > File > "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line > 558, in get_shared_data > > return FunctionSpaceData(mesh, fiat_element) > > File > "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line > 310, in __init__ > > self.bt_masks = get_bt_masks(mesh, edofs_key, fiat_element) > > File "<decorator-gen-281>", line 2, in get_bt_masks > > File > "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line > 56, in cached > > result = f(mesh, key, *args, **kwargs) > > File > "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line > 205, in get_bt_masks > > facet_dofs = horiz_facet_support_dofs(fiat_element) > > File "/home/cjc1/firedrake/src/fiat/FIAT/tensor_product.py", line 355, > in horiz_facet_support_dofs > > assert isinstance(elem.ref_el, TensorProductCell) > > AttributeError: DiscontinuousElement instance has no attribute 'ref_el' > > > > What is the right way to do this? > > > Patch FIAT/tensor_product.py to use elem.get_reference_element() rather > than using internal implementation details. > > Lawrence > -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916

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making a broken element from a Function Space
by Colin Cotter 05 Jul '16

05 Jul '16

Dear Firedrakers, I have a bit of code where I want to construct a broken function space corresponding to a given function space. My code is: Vdg_elt = BrokenElement(V.ufl_element()) Vdg = FunctionSpace(state.mesh, Vdg_elt) This returns an error: File "/home/cjc1/repositories/dcore/gusto/advection.py", line 199, in __init__ Vdg = FunctionSpace(state.mesh, Vdg_elt) File "<decorator-gen-291>", line 2, in FunctionSpace File "/home/cjc1/firedrake/src/PyOP2/pyop2/profiling.py", line 59, in wrapper return f(*args, **kwargs) File "/home/cjc1/firedrake/src/firedrake/firedrake/functionspace.py", line 131, in FunctionSpace new = impl.FunctionSpace(topology, element, name=name) File "/home/cjc1/firedrake/src/firedrake/firedrake/functionspaceimpl.py", line 245, in __init__ sdata = get_shared_data(mesh, fiat_element) File "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line 558, in get_shared_data return FunctionSpaceData(mesh, fiat_element) File "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line 310, in __init__ self.bt_masks = get_bt_masks(mesh, edofs_key, fiat_element) File "<decorator-gen-281>", line 2, in get_bt_masks File "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line 56, in cached result = f(mesh, key, *args, **kwargs) File "/home/cjc1/firedrake/src/firedrake/firedrake/functionspacedata.py", line 205, in get_bt_masks facet_dofs = horiz_facet_support_dofs(fiat_element) File "/home/cjc1/firedrake/src/fiat/FIAT/tensor_product.py", line 355, in horiz_facet_support_dofs assert isinstance(elem.ref_el, TensorProductCell) AttributeError: DiscontinuousElement instance has no attribute 'ref_el' What is the right way to do this? all the best --cjc -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916

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