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Ordering Algorithms

The following graph (sparse matrix) ordering algorithms are currently included in the Zoltan toolkit:
Nested dissection by METIS/ParMETIS
Nested dissection by Scotch/PT-Scotch
These methods produce orderings that reduce fill in sparse matrix factorizations (Cholesky). Ordering is accessed through calls to Zoltan_Order.

Third-party libraries

Currently, all ordering in Zoltan is provided through the third-party libraries METIS/ParMETIS and PT-Scotch. At least one of these must be present to use Zoltan ordering.


Ordering Parameters

While the overall behavior of Zoltan is controlled by general Zoltan parameters, the behavior of each ordering method is controlled by parameters specific to ordering which are also set by calls to Zoltan_Set_Param. Many of these parameters are specific to individual ordering algorithms, and are listed in the descriptions of the individual algorithms.  However, several have meaning across multiple ordering algorithms. These parameters are described below.
 
Parameters:
   ORDER_METHOD The order algorithm used by Zoltan is specified by this parameter. Valid values are 
"NODEND" (for nodal nested dissection by ParMETIS or METIS),
"METIS" (same as NODEND with ORDER_TYPE = local),
"PARMETIS" (same as NODEND with ORDER_TYPE = global),
"SCOTCH", (parallel or sequential depending of the value of ORDER_TYPE) and
"NONE" (for no ordering).
   ORDER_TYPE "SERIAL" or "DIST". If SERIAL is selected, the serial version of the ordering routine is used, i.e. Metis for ParMetis or Scotch for PT-Scotch. SERIAL can be selected only on non distributed graph.
ORDER_START_INDEX The start index for the permutation vectors rank and iperm. Valid values are 0 and 1.
Default Values:
ORDER_METHOD = NODEND
ORDER_TYPE = DIST
ORDER_START_INDEX = 0
REORDER = FALSE


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