7.3.4
Ordering strategy strings
Ordering strategies are available both for graphs and for meshes. An ordering
strategy is made of one or several ordering methods, which can be combined by
means of strategy operators. The strategy operators that can be used in ordering
strategies are listed below, by increasing precedence.
(
strat
)
Grouping operator. The strategy enclosed within the parentheses is treated
as a single ordering method.
/
cond
?
strat1
[
:
strat2
]
;
Condition operator. According to the result of the evaluation of condition
cond
, either
strat1
or
strat2
(if it is present) is applied. The condition applies
to the characteristics of the current node of the separators tree, and can be
built from logical and relational operators. Conditional operators are listed
below, by increasing precedence.
cond1
|
cond2
Logical or operator. The result of the condition is true if
cond1
or
cond2
are true, or both.
cond1
&
cond2
Logical and operator. The result of the condition is true only if both
cond1
and
cond2
are true.
!
cond
Logical not operator. The result of the condition is true only if
cond
is
false.
var relop val
Relational operator, where
var
is a node variable,
val
is either a node
variable or a constant of the type of variable
var
, and
relop
is one of ’
<
’,
’
=
’, and ’
>
’. The node variables are listed below, along with their types.
edge
The number of vertices of the current subgraph. Integer.
levl
The level of the subgraph in the separators tree, starting from zero
for the initial graph at the root of the tree. Integer.
load
The overall vertex load (weight) of the current subgraph. Integer.
mdeg
The maximum degree of the current subgraph. Integer.
vert
The number of vertices of the current subgraph. Integer.
method
[
{
parameters
}
]
Graph or mesh ordering method. Available ordering methods are listed below.
The currently available ordering methods are the following.
b
Blocking method. This method does not perform ordering by itself, but is used
as post-processing to cut into blocks of smaller sizes the separators or large
blocks produced by other ordering methods. This is not useful in the context of
direct solving methods, because the off-diagonal blocks created by the splitting
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