### 16.1.2. Multilevel Graph Partitioning Software - MeTiS

The public domain partitioning package MeTiS (Karypis and Kumar, 1996) uses the Multilevel Graph Partitioning Algorithm. The basic idea behind this algorithm is as follows: a graph is built containing the topology information of the mesh to be partitioned. This graph is first coarsened down to a few hundred vertices. A bisection of the resulting much coarser graph is calculated, and then the resulting partitions are projected back onto the original graph, by consecutively refining the partitions.

The MeTiS partitioner uses a fast algorithm that creates very efficient partitions. The whole process is fully automatic. However, it is unable to take advantage of coordinate direction alignment, and a substantial amount of dynamically allocated memory is required to run it (approximately 250 MB for a mesh containing 1.0E+06 nodes). If memory is a limitation, comparable results can be obtained with Optimized Recursive Coordinate Bisection. For details, see Optimized Recursive Coordinate Bisection.

MeTiS is the default partitioner used by CFX.

The Multidomain Option setting can be set to partition the mesh for each domain separately (Independent Partitioning) or to partition the mesh ignoring domains (Coupled Partitioning). Note that only domains of the same physical type (fluid/porous and solid) are coupled together for coupled partitioning.

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