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<p>Dear dune-functions developers,<br>
<br>
I am working on some code for data transfer during grid adaptation. In this I have a data vector that contains the degrees of freedom (DOF) of the grid's finite elements, modeled by a vector indexed with the index set of a dune-functions basis.<br>
Since I am losing geometric grid information of elements that disappear during a call to adapt(), I want to compute the DOFs of coarse grid entities before calling adapt(). To do this I require the finite element type of those entities, as well as the indices corresponding to the child entites of the coarse entity.<br>
<br>
The following code illustrates the process:<br>
<br>
<em>auto lv = basis.localView();<br>
// loop over all leaf elements<br>
for (auto leafElement : leafElements) {<br>
lv.bind(leafElement);<br>
const auto& node = lv.tree();<br>
const auto& fe = node.finiteElement();<br>
auto feSize = fe.size();<br>
<br>
for (std::size_t i = 0; i < feSize; ++i) {<br>
auto index = lv.index(node.localIndex(i);<br>
// save vector[index] for later use<br>
// ...<br>
}<br>
}<br>
<br>
lv.bind(coarseElement);<br>
const auto& node = lv.tree();<br>
const auto& fe = node.finiteElement();<br>
// do something with fe<br>
// ...</em><br>
<br>
Note that <em>coarseElement</em> does not access the basis's index set here.<br>
<br>
This process works for <em>Dune::UGGrid<2></em> and <em>Dune::Functions::LagrangeBasis<GridView, k></em> with <em>k</em> of any order and Dune::AlbertaGrid<2,2> with <em>Dune::Functions::LagrangeBasis<GridView, 1></em>.<br>
<br>
However it fails for Dune::AlbertaGrid<2,2> with <em>Dune::Functions::LagrangeBasis<GridView, k></em> with <em>k ≠ 1</em> at:<br>
<strong>dune/grid/albertagrid/indexsets.hh:482</strong>: <em>Assertion `(subIndex >= 0) && (subIndex < size( codim ))' failed.</em><br>
Deactivating the assertion prevents the crash and makes my code run just fine.<br>
<br>
The issue above seems to be caused by <strong>dune/functions/functionspacebases/defaultlocalview.hh:72:</strong><br>
void bind(const Element& e)<br>
{<br>
element_ = e;<br>
bindTree(tree_, element_);<br>
nodeIndexSet_.bind(tree_);<br>
indices_.resize(size());<br>
Hybrid::ifElse(<br>
Std::is_detected<hasIndices,NodeIndexSet>{},<br>
[&](auto id) {<br>
id(nodeIndexSet_).indices(indices_.begin());<br>
},<br>
[&](auto id) {<br>
for (size_type i = 0 ; i < this->size() ; ++i)<br>
indices_[i] = id(nodeIndexSet_).index(i);<br>
});<br>
}<br>
This tries to access the index set on <em>coarseElement</em>, which is not defined and not needed within my code either.<br>
<strong>Dune-functions 2.5</strong> had a seperate binding mechanism for the local view and index sets, providing only the method<br>
<em>void bind(const Element& e)<br>
{<br>
element_ = e;<br>
bindTree(tree_, element_);<br>
}</em><br>
which is completely sufficient for my purpose.<br>
<br>
<br>
<u>My question now is:</u><br>
- Is this behaviour intended or is this a bug in either <strong>defaultlocalview.hh</strong> or <strong>AlbertaGrid</strong>?<br>
- If it is intended, is there a way to only bind the local view without binding the index set, like in v2.5?<br>
<br>
<br>
Thanks for your attention and helpful answers!<br>
<br>
Felix Müller<br>
<br>
<br>
PS: You will find a small file reproducing the error attached. A filename for the AlbertaReader must be provided as argument to the main method. I have used <strong>dune-grid/doc/grids/amc/grid-2-2.amc</strong> as grid file for my tests.</p>
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