ufz/ogs — pull request #549 by endJunction (2014-12-11 17:50:00+00:00)
Title: Node adjacency table

I have started a creation of a node adjacency table. The reason for this were mainly the endless memory reallocations in LIS. (When creating matrix there, the data is first written into a buffer, which has to be allocated). Here again the net gain is:
- measured on the ExternalData/.../cube_1e4: 5.40s on master vs. 0.25s this branch.
- measured on the ExternalData/.../cube_1e5: 820s on master vs. 2.50s this branch.

The (`createTable`) algorithm stores adjacent nodes to every node in a vector of vector structure. The nodes i and j are adjacent iff they are shared by an element.
Current implementation provides only the `getNodeDegree()` function, because I don't know the required access pattern for creation of CRS matrices etc.

I also add a `setMatrixSparsity()` function (empty implementation by default), which is currently used in the lis interface. (Unfortunatly a little too technical...)

Computation and application are in the `GroundwaterFlowProcess`.