```      SUBROUTINE SPPTRS( UPLO, N, NRHS, AP, 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, LDB, N, NRHS
*     ..
*     .. Array Arguments ..
REAL               AP( * ), B( LDB, * )
*     ..
*
*  Purpose
*  =======
*
*  SPPTRS solves a system of linear equations A*X = B with a symmetric
*  positive definite matrix A in packed storage using the Cholesky
*  factorization A = U**T*U or A = L*L**T computed by SPPTRF.
*
*  Arguments
*  =========
*
*  UPLO    (input) CHARACTER*1
*          = 'U':  Upper triangle of A is stored;
*          = 'L':  Lower triangle of A is stored.
*
*  N       (input) INTEGER
*          The order of the matrix A.  N >= 0.
*
*  NRHS    (input) INTEGER
*          The number of right hand sides, i.e., the number of columns
*          of the matrix B.  NRHS >= 0.
*
*  AP      (input) REAL array, dimension (N*(N+1)/2)
*          The triangular factor U or L from the Cholesky factorization
*          A = U**T*U or A = L*L**T, packed columnwise in a linear
*          array.  The j-th column of U or L is stored in the array AP
*          as follows:
*          if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j;
*          if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n.
*
*  B       (input/output) REAL 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            I
*     ..
*     .. External Functions ..
LOGICAL            LSAME
EXTERNAL           LSAME
*     ..
*     .. External Subroutines ..
EXTERNAL           STPSV, 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( NRHS.LT.0 ) THEN
INFO = -3
ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
INFO = -6
END IF
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'SPPTRS', -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 I = 1, NRHS
*
*           Solve U'*X = B, overwriting B with X.
*
CALL STPSV( 'Upper', 'Transpose', 'Non-unit', N, AP,
\$                  B( 1, I ), 1 )
*
*           Solve U*X = B, overwriting B with X.
*
CALL STPSV( 'Upper', 'No transpose', 'Non-unit', N, AP,
\$                  B( 1, I ), 1 )
10    CONTINUE
ELSE
*
*        Solve A*X = B where A = L*L'.
*
DO 20 I = 1, NRHS
*
*           Solve L*Y = B, overwriting B with X.
*
CALL STPSV( 'Lower', 'No transpose', 'Non-unit', N, AP,
\$                  B( 1, I ), 1 )
*
*           Solve L'*X = Y, overwriting B with X.
*
CALL STPSV( 'Lower', 'Transpose', 'Non-unit', N, AP,
\$                  B( 1, I ), 1 )
20    CONTINUE
END IF
*
RETURN
*
*     End of SPPTRS
*
END

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