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elementwise_integral doesn't respect quadrature rules #215

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inducer opened this issue Jan 26, 2022 · 1 comment · May be fixed by #216
Open

elementwise_integral doesn't respect quadrature rules #215

inducer opened this issue Jan 26, 2022 · 1 comment · May be fixed by #216

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@inducer
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inducer commented Jan 26, 2022 •
edited

As implemented here:

grudge/grudge/reductions.py

Lines 455 to 470 in f3d986b

if len(args) == 1:
vec, = args
dd = dof_desc.DOFDesc("vol", dof_desc.DISCR_TAG_BASE)
elif len(args) == 2:
dd, vec = args
else:
raise TypeError("invalid number of arguments")
dd = dof_desc.as_dofdesc(dd)
from grudge.op import _apply_mass_operator
ones = dcoll.discr_from_dd(dd).zeros(vec.array_context) + 1.0
return elementwise_sum(
dcoll, dd, vec * _apply_mass_operator(dcoll, dd, dd, ones)
)

It always falls into the mass-matrix logic, which is valid for nodal-interpolatory grids, but not quadrature grids.

cc @thomasgibson
@inducer
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inducer commented Jan 26, 2022 •
edited

Could implement, per group, as:

res = DOFArray(
    dof_array.array_context,
    tuple([
        actx.np.einsum("ei,i,ei->e",
            dof_array.data[i], quad_weights, area_elements.data[i]
            ).reshape(-1, 1)
        for grp, vec_grp_ary, ae_grp_ary in zip(
            discr.groups, vec.data, area_elements.data
    ])

@thomasgibson thomasgibson linked a pull request Jan 28, 2022 that will close this issue
Patch for integral computations when using overintegration #216
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Patch for integral computations when using overintegration inducer/grudge
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@inducer