(3M) Calculator User Manual

of large diagonal blocks are likely to be filled at facto ring time. However, in
the context of incomplete solving methods such as ILU(k) [29], it can lead
to a significant reduction of the required memory space and time, because it
helps carving large triangular blocks. The parameters of the blocking method
are described below.
cmin=s ize
Set the minimum size of the resulting subblocks, in number o f columns.
Blocks larger than twice this minimum size are cut into sub-blocks of
equal sizes (within one), having a number of c olumns comprised between
size and 2size.
The definition of size depends on the size of the graph to order. Large
graphs cannot afford very small va lues, becaus e the number of blocks
becomes much too large and limits the acceleration of BLAS 3 routines,
while large values do not help reducing enough the complexity of ILU(k)
solving.
strat=strat
Ordering strategy to be performed. After the ordering strategy is applied,
the resulting separa tors tree is traversed and all of the column blo cks
that are larger than 2size are split into smaller column blocks, without
changing the ordering that has been computed.
c Compres sion method [2]. The parameters of the compres sion method are
listed below.
rat=rat
Set the compressio n ratio over which graphs and meshes will not be
compressed. Useful values range between 0.7 and 0.8.
cpr=st rat
Ordering strategy to use on the compres sed graph or mesh if its size is
below the compression ratio times the size of the original graph or mesh.
unc=st rat
Ordering strategy to use on the original graph or mesh if the size of the
compressed graph or mesh were above the compression ratio times the
size of the original graph or mesh.
d Block Halo Approximate Minimum Degree method [47]. The parameters of
the Halo Approximate Minimum Degre e method are listed below. The Block
Halo Approximate Minimum Fill method, described below, is more efficient
and should b e preferred.
cmin=s ize
Minimum number of columns per co lumn block. All column blocks of
width smaller than size are amalgamated to their parent c olumn block in
the elimination tree, provided that it does not violate the cmax c onstraint.
cmax=s ize
Maximum number of column blocks over which some column block will
not a malgamate one of its desce ndents in the eliminatio n tree. This
parameter is mainly designed to provide an upper bound for block s ize
in the context of BLAS3 computations ; else, a huge value should be
provided.
64