NAME¶

SGBTRS - solves a system of linear equations A * X = B or A' * X = B with a general band matrix A using the LU factorization computed by SGBTRF

SYNOPSIS¶

SUBROUTINE SGBTRS(

TRANS, N, KL, KU, NRHS, AB, LDAB, IPIV, B, LDB, INFO )

CHARACTER TRANS INTEGER INFO, KL, KU, LDAB, LDB, N, NRHS INTEGER IPIV( * ) REAL AB( LDAB, * ), B( LDB, * )

PURPOSE¶

SGBTRS solves a system of linear equations
A * X = B or A' * X = B with a general band matrix A using the LU factorization computed by SGBTRF.

ARGUMENTS¶

TRANS (input) CHARACTER*1

Specifies the form of the system of equations. = 'N': A * X = B (No transpose)
= 'T': A'* X = B (Transpose)
= 'C': A'* X = B (Conjugate transpose = Transpose)

N (input) INTEGER

The order of the matrix A. N >= 0.

KL (input) INTEGER

The number of subdiagonals within the band of A. KL >= 0.

KU (input) INTEGER

The number of superdiagonals within the band of A. KU >= 0.

NRHS (input) INTEGER

The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.

AB (input) REAL array, dimension (LDAB,N)

Details of the LU factorization of the band matrix A, as computed by SGBTRF. U is stored as an upper triangular band matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and the multipliers used during the factorization are stored in rows KL+KU+2 to 2*KL+KU+1.

LDAB (input) INTEGER

The leading dimension of the array AB. LDAB >= 2*KL+KU+1.

IPIV (input) INTEGER array, dimension (N)

The pivot indices; for 1 <= i <= N, row i of the matrix was interchanged with row IPIV(i).

B (input/output) REAL array, dimension (LDB,NRHS)

On entry, the right hand side matrix B. On exit, the solution matrix X.

LDB (input) INTEGER

The leading dimension of the array B. LDB >= max(1,N).

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value