(3M) Calculator User Manual

such as ﬂoating point exceptions, which could not be properly handled by the

calling software.

7.3.2 Mapping strategy strings

At the time being, mapping methods only apply to graphs, as there is not yet a mesh

mapping tool in the Scotch package. Mapping s trategies are made of methods,

with optional parameters enclosed between curly br aces, and separated by commas,

in the form of method[{parameters}] . The currently available mapping methods

are the following.

m Multi-level method. The parameters of the multi-level method are listed be-

low.

asc=st rat

Set the strategy that is used to r e ﬁne the mappings obtained at ascending

levels of the uncoar sening phase by pr ojection of the mappings computed

for coarser graphs. This strategy is not applied to the coarsest graph,

for which only the low strategy is used.

low=st rat

Set the strategy that is used to compute the mapping of the coarsest

graph, at the lowest level of the coarsening process.

rat=rat

Set the threshold maximum coarsening ratio over which graphs are no

longer coarsened. The ratio of any given coarsening cannot be less that

0.5 (case of a perfect matching), and cannot be greater than 1.0. Co ars-

ening stops when either the coarsening ratio is above the maximum coars-

ening ratio, or the graph has fewer ve rtices than the minimum number

of vertices allowed.

type=type

Set the type of matching that is used to coarse n the graphs. type is h for

heavy-edge matching, or s fo r scan (ﬁrst-ﬁt) matching.

vert=nbr

Set the threshold under which graphs are no longer coarsened. Coa rsen-

ing stops when either the coarsening ratio is above the maximum coars-

ening ratio, or the graph would have fewer ver tices than the minimum

number of vertices allowe d. When the target architecture is a va riable-

sized architecture, coarsening stops when the coarsened graph would have

less than nbr vertices. When the target architecture is a regular, ﬁxed-

size, architecture, coarsening stops when e ach subdomain would have less

than nbr vertices, that is, when the size of the coars e ned graph would

have less than nbr × domnnbr vertices, where domnnbr is the number of

vertices in the target architecture.

r Dual Recursive Bipartitioning mapping algorithm, as deﬁned in section 3.1.3.

The parameters of the DRB mapping method are listed below.

job=tie

The tie ﬂag deﬁnes how new jobs are stor e d in job pools.

t Tie job pools together. Subjobs are stored in same poo l a s their par-

ent job. T his is the default behavior, as it proves the most eﬃcient

in practice.