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Operators and Keywords

Function List:

C++ API

: spparms ()
: vals = spparms ()
: [keys, vals] = spparms ()
: val = spparms (key)
: spparms (vals)
: spparms ("default")
: spparms ("tight")
: spparms (key, val)

Query or set the parameters used by the sparse solvers and factorization functions.

The first four calls above get information about the current settings, while the others change the current settings. The parameters are stored as pairs of keys and values, where the values are all floats and the keys are one of the following strings:

‘spumoni’

Printing level of debugging information of the solvers (default 0)

‘ths_rel’

Included for compatibility. Not used. (default 1)

‘ths_abs’

Included for compatibility. Not used. (default 1)

‘exact_d’

Included for compatibility. Not used. (default 0)

‘supernd’

Included for compatibility. Not used. (default 3)

‘rreduce’

Included for compatibility. Not used. (default 3)

‘wh_frac’

Included for compatibility. Not used. (default 0.5)

‘autommd’

Flag whether the LU/QR and the ’\’ and ’/’ operators will automatically use the sparsity preserving mmd functions (default 1)

‘autoamd’

Flag whether the LU and the ’\’ and ’/’ operators will automatically use the sparsity preserving amd functions (default 1)

‘piv_tol’

The pivot tolerance of the UMFPACK solvers (default 0.1)

‘sym_tol’

The pivot tolerance of the UMFPACK symmetric solvers (default 0.001)

‘bandden’

The density of nonzero elements in a banded matrix before it is treated by the LAPACK banded solvers (default 0.5)

‘umfpack’

Flag whether the UMFPACK or mmd solvers are used for the LU, ’\’ and ’/’ operations (default 1)

The value of individual keys can be set with spparms (key, val). The default values can be restored with the special keyword "default". The special keyword "tight" can be used to set the mmd solvers to attempt a sparser solution at the potential cost of longer running time.

See also: chol, colamd, lu, qr, symamd.

Package: octave