Previous: cgbtrf Up: ../lapack-c.html Next: cgebak

# cgbtrs

```
NAME
CGBTRS - solve a system of linear equations  A * X = B, A**T
* X = B, or A**H * X = B with a general band matrix A using
the LU factorization computed by CGBTRF

SYNOPSIS
SUBROUTINE CGBTRS( TRANS, N, KL, KU, NRHS, AB, LDAB, IPIV,
B, LDB, INFO )

CHARACTER      TRANS

INTEGER        INFO, KL, KU, LDAB, LDB, N, NRHS

INTEGER        IPIV( * )

COMPLEX        AB( LDAB, * ), B( LDB, * )

PURPOSE
CGBTRS solves a system of linear equations
A * X = B,  A**T * X = B,  or  A**H * X = B with a gen-
eral band matrix A using the LU factorization computed by
CGBTRF.

ARGUMENTS
TRANS   (input) CHARACTER*1
Specifies the form of the system of equations.  =
'N':  A * X = B     (No transpose)
= 'T':  A**T * X = B  (Transpose)
= 'C':  A**H * X = B  (Conjugate 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) COMPLEX array, dimension (LDAB,N)
Details of the LU factorization of the band matrix
A, as computed by CGBTRF.  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) COMPLEX 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
```