# naginterfaces.library.lapacklin.dsytrs¶

naginterfaces.library.lapacklin.dsytrs(uplo, a, ipiv, b)[source]

dsytrs solves a real symmetric indefinite system of linear equations with multiple right-hand sides,

where has been factorized by dsytrf().

For full information please refer to the NAG Library document for f07me

https://www.nag.com/numeric/nl/nagdoc_29/flhtml/f07/f07mef.html

Parameters
uplostr, length 1

Specifies how has been factorized.

, where is upper triangular.

, where is lower triangular.

afloat, array-like, shape

Details of the factorization of , as returned by dsytrf().

ipivint, array-like, shape

Details of the interchanges and the block structure of , as returned by dsytrf().

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

dsytrs is used to solve a real symmetric indefinite system of linear equations , this function must be preceded by a call to dsytrf() which computes the Bunch–Kaufman factorization of .

If , , where is a permutation matrix, is an upper triangular matrix and is a symmetric block diagonal matrix with and blocks; the solution is computed by solving and then .

If , , where is a lower triangular matrix; 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