SPPARMS

Set parameters for sparse matrix routines.

SPPARMS('key',value) sets one or more of the "tunable" parameters

used in the sparse linear equation operators, \ and /, and the

minimum degree orderings, COLMMD and SYMMMD.

SPPARMS, by itself, prints a description of the current settings.

If no input argument is present, values = SPPARMS returns a

vector whose components give the current settings.

[keys,values] = SPPARMS returns that vector, and also returns

a character matrix whose rows are the keywords for the parameters.

SPPARMS(values), with no output argument, sets all the parameters

to the values specified by the argument vector.

value = SPPARMS('key') returns the current setting of one parameter.

SPPARMS('default') sets all the parameters to their default settings.

SPPARMS('tight') sets the minimum degree ordering parameters to their

"tight" settings, which may lead to orderings with less fill-in, but

which makes the ordering functions themselves use more execution time.

The parameters with the default and "tight" values are:

keyword       default       tight

values(1)     'spumoni'      0

values(2)     'thr_rel'      1.1          1.0

values(3)     'thr_abs'      1.0          0.0

values(4)     'exact_d'      0            1

values(5)     'supernd'      3            1

values(6)     'rreduce'      3            1

values(7)     'wh_frac'      0.5          0.5

values(8)     'autommd'      1

values(9)     'aug_rel'      0.001

values(10)    'aug_abs'      0

The meanings of the parameters are

spumoni:  The Sparse Monitor Flag controls diagnostic output;

0 means none, 1 means some, 2 means too much.

thr_rel,

thr_abs:  Minimum degree threshold is thr_rel*mindegree + thr_abs.

exact_d:  Nonzero to use exact degrees in minimum degree,

Zero to use approximate degrees.

supernd:  If > 0, MMD amalgamates supernodes every supernd stages.

rreduce:  If > 0, MMD does row reduction every rreduce stages.

wh_frac:  Rows with density > wh_frac are ignored in COLMMD.

autommd:  Nonzero to use minimum degree orderings with \ and /.

aug_rel,

aug_abs: Residual scaling parameter for augmented equations is

aug_rel*max(max(abs(A))) + aug_abs.

For example, aug_rel = 0, aug_abs = 1 puts an unscaled

identity matrix in the (1,1) block of the augmented matrix.