Documentation

spparms

Set parameters for sparse matrix routines

Syntax

spparms('key',value)
spparms
values = spparms
[keys,values] = spparms
spparms(values)
value = spparms('key')
spparms('default')
spparms('tight')

Description

spparms('key',value)sets one or more of thetunableparameters used in the sparse routines. In ordinary use, you should never need to deal with this function.

The meanings of thekeyparameters are

'spumoni'

Sparse Monitor flag:
0

Produces no diagnostic output, the default
1

Produces information about choice of algorithm based on matrix structure, and about storage allocation
2

Also produces very detailed information about the sparse matrix algorithms
'thr_rel',
'thr_abs'

Minimum degree threshold isthr_rel*mindegree + thr_abs.
'exact_d'

Nonzero to use exact degrees in minimum degree. Zero to use approximate degrees.
'supernd'

If positive, minimum degree amalgamates the supernodes everysuperndstages.
'rreduce'

If positive, minimum degree does row reduction everyrreducestages.
'wh_frac'

Rows withdensity > wh_fracare ignored incolmmd.
'autommd'

Nonzero to use minimum degree (MMD) orderings with QR-based \ and/.
'autoamd'

Nonzero to usecolamdordering with the LU-based \ and /, and to useamdwith Cholesky-based \ and /.
'piv_tol'

Pivot tolerance used by the LU-based \ and /.
'bandden'

Band density used by \ and / for banded matrices. Band density is defined as (# nonzeros in the band)/(# nonzeros in a full band). Ifbandden = 1.0, never use band solver. Ifbandden = 0.0, always use band solver. Default is0.5.
'umfpack'

Nonzero to use UMFPACK instead of the v4 LU-based solver in\and/.
'sym_tol'

Symmetric pivot tolerance. Seelufor more information about the role of the symmetric pivot tolerance.

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

values = spparmsreturns a vector whose components give the current settings.

[keys,values] = spparmsreturns 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 theirtightsettings, which can lead to orderings with less fill-in, but which make the ordering functions themselves use more execution time.

The key parameters fordefaultandtightsettings are

Keyword

Default

Tight
values(1) 'spumoni'

0.0
values(2) 'thr_rel'

1.1

1.0
values(3) 'thr_abs'

1.0

0.0
values(4) 'exact_d'

0.0

1.0
values(5) 'supernd'

3.0

1.0
values(6) 'rreduce'

3.0

1.0
values(7) 'wh_frac'

0.5

0.5
values(8) 'autommd'

1.0
values(9) 'autoamd'

1.0
values(10) 'piv_tol'

0.1
values(11) 'bandden'

0.5
values(12) 'umfpack'

1.0
values(13) 'sym_tol'

0.001

See Also

||||

Introduced before R2006a

Was this topic helpful?
MATLAB Documentation
Other Documentation
金宝app

Try MATLAB, Simulink, and Other Products

Get trial now