[Dune] Coarsening of ALUGrid very slow

[Uli Sack]

oops, by the way it's a 2D grid. and the ALU-version 1.13.

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* Uli Sack                     ** email: usack at math.fu-berlin.de       *
* Freie Universität Berlin     ** phone: + 49 (30) 838 75250           *
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