Correct number of candidates for prolong/restrict on extruded meshes

[pbrubeck]

---

name: "Bug fix or new feature"
description: ''
title: ''
labels: ''
assignees: ''

---

Description

Prolongation and restriction kernels were incorrectly looping into out of bounds coarse basis functions in the extruded case. The logic added in 86e6ca3 was only correct for the injection kernel. So far the tests only considered cases that terminated the loop before going out of bounds. When the children cells fall out of the parent coarse cell, we access out of bounds memory, which utimately causes a nan to be returned on these cases.

I also added a test with a deformed mesh hierarchy, although inject still breaks without producing nan for degree > 1 and only on some types of cells (works on interval x interval).

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[ksagiyam]

So what was level_ratio?

[pbrubeck]

So what was level_ratio?

It's simply the ratio of the column height of the fine and coarse meshes.