!>
!> SGBT01 reconstructs a band matrix A from its L*U factorization and
!> computes the residual:
!>    norm(L*U - A) / ( N * norm(A) * EPS ),
!> where EPS is the machine epsilon.
!>
!> The expression L*U - A is computed one column at a time, so A and
!> AFAC are not modified.
!> 

M

!>          M is INTEGER
!>          The number of rows of the matrix A.  M >= 0.
!> 

N

!>          N is INTEGER
!>          The number of columns of the matrix A.  N >= 0.
!> 

KL

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

KU

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

A

!>          A is REAL array, dimension (LDA,N)
!>          The original matrix A in band storage, stored in rows 1 to
!>          KL+KU+1.
!> 

LDA

!>          LDA is INTEGER.
!>          The leading dimension of the array A.  LDA >= max(1,KL+KU+1).
!> 

AFAC

!>          AFAC is REAL array, dimension (LDAFAC,N)
!>          The factored form of the matrix A.  AFAC contains the banded
!>          factors L and U from the L*U factorization, 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.  See SGBTRF for further details.
!> 

LDAFAC

!>          LDAFAC is INTEGER
!>          The leading dimension of the array AFAC.
!>          LDAFAC >= max(1,2*KL*KU+1).
!> 

IPIV

!>          IPIV is INTEGER array, dimension (min(M,N))
!>          The pivot indices from SGBTRF.
!> 

WORK

!>          WORK is REAL array, dimension (2*KL+KU+1)
!> 

RESID

!>          RESID is REAL
!>          norm(L*U - A) / ( N * norm(A) * EPS )
!> 

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