(3M) Calculator User Manual

and “Data”, allow callers to retrieve informa tion from opaque structures.
In all of the following, whenever arrays are defined, passed, and accessed, it
is assumed that the first element of these arrays is always labeled as baseval,
whether baseval is s e t to 0 (for C-style arrays) or 1 (for Fortran-s tyle a rrays).
Scotch internally manages with ba se va lues and array pointers so as to pro cess
these arrays accordingly.
7.2.1 Architecture format
Targ et architecture str uctur e s are completely opaque. The only way to describe an
architecture is by means of a graph passed to the SCOTCH archBuild routine.
7.2.2 Graph format
Source graphs are describe d by means of adjacency lists. The description of a g raph
requires several SCOTCH
Num scalars and arrays, as shown in Figures 16 and 17. They
have the following meaning:
baseval
Base value for all array indexings.
vertnbr
Number of vertices in graph.
edgenbr
Number of arcs in graph. Since edges are repre sented by both of their ends,
the number of edge data in the graph is twice the number of graph edges.
verttab
Array of start indices in edgetab of vertex adjacency sub-arrays.
vendtab
Array of after-last indices in edgetab of vertex adjacency sub-arrays. For any
vertex i, with baseval ≤ i < (baseval+vertnbr), vendtab[i]−verttab[i]
is the degree of vertex i, and the indices of the neighbors of i are store d in
edgetab from edgetab[verttab[i]] to edgetab[vendtab[i]−1], inclusive.
When all vertex adjacency lists are sto red in order in edgetab, it is possible to
save memory by not allocating the physical memory for vendtab. In this case,
illustrated in Figure 16, verttab is of size vertnbr+ 1 and vendtab points to
verttab + 1. This case is referred to as the “compact edge array” case, such
that verttab is sorted in ascending order, verttab[baseval] = baseval and
verttab[baseval + vertnbr] = (baseval + edgenbr).
velotab
Optional array, of size vertnbr, holding the integer load as sociated with every
vertex.
edgetab
Array, of a size equal at least to (max
i
(vendtab[i]) − baseval), holding the
adjacency array of every vertex.
edlotab
Optional array, of a size equal at least to (max
i
(vendtab[i]) − baseval),
holding the integer load associated with every arc. Matching arcs should
always have identical loads.
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