Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A comparison of element agglomeration algorithms for unstructured
  geometric multigrid   This paper compares the performance of seven different element agglomeration
algorithms on unstructured triangular/tetrahedral meshes when used as part of a
geometric multigrid. Five of these algorithms come from the literature on AMGe
multigrid and mesh partitioning methods. The resulting multigrid schemes are
tested matrix-free on two problems in 2D and 3D taken from radiation transport
applications; one of which is in the diffusion limit. In two dimensions all
coarsening algorithms result in multigrid methods which perform similarly, but
in three dimensions aggressive element agglomeration performed by METIS
produces the shortest runtimes and multigrid setup times.

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The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an