```      SUBROUTINE CPBTRS( UPLO, N, KD, NRHS, AB, LDAB, B, LDB, INFO )
*
*  -- LAPACK routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
CHARACTER          UPLO
INTEGER            INFO, KD, LDAB, LDB, N, NRHS
*     ..
*     .. Array Arguments ..
COMPLEX            AB( LDAB, * ), B( LDB, * )
*     ..
*
*  Purpose
*  =======
*
*  CPBTRS solves a system of linear equations A*X = B with a Hermitian
*  positive definite band matrix A using the Cholesky factorization
*  A = U**H*U or A = L*L**H computed by CPBTRF.
*
*  Arguments
*  =========
*
*  UPLO    (input) CHARACTER*1
*          = 'U':  Upper triangular factor stored in AB;
*          = 'L':  Lower triangular factor stored in AB.
*
*  N       (input) INTEGER
*          The order of the matrix A.  N >= 0.
*
*  KD      (input) INTEGER
*          The number of superdiagonals of the matrix A if UPLO = 'U',
*          or the number of subdiagonals if UPLO = 'L'.  KD >= 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)
*          The triangular factor U or L from the Cholesky factorization
*          A = U**H*U or A = L*L**H of the band matrix A, stored in the
*          first KD+1 rows of the array.  The j-th column of U or L is
*          stored in the j-th column of the array AB as follows:
*          if UPLO ='U', AB(kd+1+i-j,j) = U(i,j) for max(1,j-kd)<=i<=j;
*          if UPLO ='L', AB(1+i-j,j)    = L(i,j) for j<=i<=min(n,j+kd).
*
*  LDAB    (input) INTEGER
*          The leading dimension of the array AB.  LDAB >= KD+1.
*
*  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
*
*  =====================================================================
*
*     .. Local Scalars ..
LOGICAL            UPPER
INTEGER            J
*     ..
*     .. External Functions ..
LOGICAL            LSAME
EXTERNAL           LSAME
*     ..
*     .. External Subroutines ..
EXTERNAL           CTBSV, XERBLA
*     ..
*     .. Intrinsic Functions ..
INTRINSIC          MAX
*     ..
*     .. Executable Statements ..
*
*     Test the input parameters.
*
INFO = 0
UPPER = LSAME( UPLO, 'U' )
IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
INFO = -1
ELSE IF( N.LT.0 ) THEN
INFO = -2
ELSE IF( KD.LT.0 ) THEN
INFO = -3
ELSE IF( NRHS.LT.0 ) THEN
INFO = -4
ELSE IF( LDAB.LT.KD+1 ) THEN
INFO = -6
ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
INFO = -8
END IF
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'CPBTRS', -INFO )
RETURN
END IF
*
*     Quick return if possible
*
IF( N.EQ.0 .OR. NRHS.EQ.0 )
\$   RETURN
*
IF( UPPER ) THEN
*
*        Solve A*X = B where A = U'*U.
*
DO 10 J = 1, NRHS
*
*           Solve U'*X = B, overwriting B with X.
*
CALL CTBSV( 'Upper', 'Conjugate transpose', 'Non-unit', N,
\$                  KD, AB, LDAB, B( 1, J ), 1 )
*
*           Solve U*X = B, overwriting B with X.
*
CALL CTBSV( 'Upper', 'No transpose', 'Non-unit', N, KD, AB,
\$                  LDAB, B( 1, J ), 1 )
10    CONTINUE
ELSE
*
*        Solve A*X = B where A = L*L'.
*
DO 20 J = 1, NRHS
*
*           Solve L*X = B, overwriting B with X.
*
CALL CTBSV( 'Lower', 'No transpose', 'Non-unit', N, KD, AB,
\$                  LDAB, B( 1, J ), 1 )
*
*           Solve L'*X = B, overwriting B with X.
*
CALL CTBSV( 'Lower', 'Conjugate transpose', 'Non-unit', N,
\$                  KD, AB, LDAB, B( 1, J ), 1 )
20    CONTINUE
END IF
*
RETURN
*
*     End of CPBTRS
*
END

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