DGBTRS(l) ) DGBTRS(l)NAME
DGBTRS - solve a system of linear equations A * X = B or A' * X = B
with a general band matrix A using the LU factorization computed by
DGBTRF
SYNOPSIS
SUBROUTINE DGBTRS( TRANS, N, KL, KU, NRHS, AB, LDAB, IPIV, B, LDB, INFO
)
CHARACTER TRANS
INTEGER INFO, KL, KU, LDAB, LDB, N, NRHS
INTEGER IPIV( * )
DOUBLE PRECISION AB( LDAB, * ), B( LDB, * )
PURPOSE
DGBTRS 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 DGBTRF.
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) DOUBLE PRECISION array, dimension (LDAB,N)
Details of the LU factorization of the band matrix A, as com‐
puted by DGBTRF. 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) DOUBLE PRECISION 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
LAPACK version 3.0 15 June 2000 DGBTRS(l)
