naginterfaces.library.lapacklin.dgetrs

naginterfaces.library.lapacklin.dgetrs(trans, a, ipiv, b)[source]

dgetrs solves a real system of linear equations with multiple right-hand sides,

where has been factorized by dgetrf().

For full information please refer to the NAG Library document for f07ae

https://www.nag.com/numeric/nl/nagdoc_27.3/flhtml/f07/f07aef.html

Parameters
transstr, length 1

Indicates the form of the equations.

is solved for .

or

is solved for .

afloat, array-like, shape

The factorization of , as returned by dgetrf().

ipivint, array-like, shape

The pivot indices, as returned by dgetrf().

bfloat, array-like, shape

The right-hand side matrix .

Returns
bfloat, ndarray, shape

The solution matrix .

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: , or .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: .

Notes

dgetrs is used to solve a real system of linear equations or , the function must be preceded by a call to dgetrf() which computes the factorization of as . The solution is computed by forward and backward substitution.

If , the solution is computed by solving and then .

If or , the solution is computed by solving and then .

References

Golub, G H and Van Loan, C F, 1996, Matrix Computations, (3rd Edition), Johns Hopkins University Press, Baltimore