          SUBROUTINE DPBTRS( 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 ..
          DOUBLE PRECISION   AB( LDAB, * ), B( LDB, * )
    *     ..
    *
    *  Purpose
    *  =======
    *
    *  DPBTRS solves a system of linear equations A*X = B with a symmetric
    *  positive definite band matrix A using the Cholesky factorization
    *  A = U**T*U or A = L*L**T computed by DPBTRF.
    *
    *  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) DOUBLE PRECISION array, dimension (LDAB,N)
    *          The triangular factor U or L from the Cholesky factorization
    *          A = U**T*U or A = L*L**T 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) 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
    *
    *  =====================================================================
    *
    *     .. Local Scalars ..
          LOGICAL            UPPER
          INTEGER            J
    *     ..
    *     .. External Functions ..
          LOGICAL            LSAME
          EXTERNAL           LSAME
    *     ..
    *     .. External Subroutines ..
          EXTERNAL           DTBSV, 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( 'DPBTRS', -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 DTBSV( 'Upper', 'Transpose', 'Non-unit', N, KD, AB,
         $                  LDAB, B( 1, J ), 1 )
    *
    *           Solve U*X = B, overwriting B with X.
    *
                CALL DTBSV( '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 DTBSV( 'Lower', 'No transpose', 'Non-unit', N, KD, AB,
         $                  LDAB, B( 1, J ), 1 )
    *
    *           Solve L'*X = B, overwriting B with X.
    *
                CALL DTBSV( 'Lower', 'Transpose', 'Non-unit', N, KD, AB,
         $                  LDAB, B( 1, J ), 1 )
       20    CONTINUE
          END IF
    *
          RETURN
    *
    *     End of DPBTRS
    *
          END