#include "blaswrap.h"
#include "f2c.h"

/* Subroutine */ int sppsv_(char *uplo, integer *n, integer *nrhs, real *ap, 
	real *b, integer *ldb, integer *info)
{
/*  -- LAPACK driver routine (version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       March 31, 1993   


    Purpose   
    =======   

    SPPSV computes the solution to a real system of linear equations   
       A * X = B,   
    where A is an N-by-N symmetric positive definite matrix stored in   
    packed format and X and B are N-by-NRHS matrices.   

    The Cholesky decomposition is used to factor A as   
       A = U**T* U,  if UPLO = 'U', or   
       A = L * L**T,  if UPLO = 'L',   
    where U is an upper triangular matrix and L is a lower triangular   
    matrix.  The factored form of A is then used to solve the system of   
    equations A * X = B.   

    Arguments   
    =========   

    UPLO    (input) CHARACTER*1   
            = 'U':  Upper triangle of A is stored;   
            = 'L':  Lower triangle of A is stored.   

    N       (input) INTEGER   
            The number of linear equations, i.e., 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/output) REAL array, dimension (N*(N+1)/2)   
            On entry, the upper or lower triangle of the symmetric matrix   
            A, packed columnwise in a linear array.  The j-th column of A   
            is stored in the array AP as follows:   
            if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;   
            if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.   
            See below for further details.   

            On exit, if INFO = 0, the factor U or L from the Cholesky   
            factorization A = U**T*U or A = L*L**T, in the same storage   
            format as A.   

    B       (input/output) REAL array, dimension (LDB,NRHS)   
            On entry, the N-by-NRHS right hand side matrix B.   
            On exit, if INFO = 0, the N-by-NRHS 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   
            > 0:  if INFO = i, the leading minor of order i of A is not   
                  positive definite, so the factorization could not be   
                  completed, and the solution has not been computed.   

    Further Details   
    ===============   

    The packed storage scheme is illustrated by the following example   
    when N = 4, UPLO = 'U':   

    Two-dimensional storage of the symmetric matrix A:   

       a11 a12 a13 a14   
           a22 a23 a24   
               a33 a34     (aij = conjg(aji))   
                   a44   

    Packed storage of the upper triangle of A:   

    AP = [ a11, a12, a22, a13, a23, a33, a14, a24, a34, a44 ]   

    =====================================================================   


       Test the input parameters.   

       Parameter adjustments */
    /* System generated locals */
    integer b_dim1, b_offset, i__1;
    /* Local variables */
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int xerbla_(char *, integer *), spptrf_(
	    char *, integer *, real *, integer *), spptrs_(char *, 
	    integer *, integer *, real *, real *, integer *, integer *);

    --ap;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1 * 1;
    b -= b_offset;

    /* Function Body */
    *info = 0;
    if (! lsame_(uplo, "U") && ! lsame_(uplo, "L")) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*nrhs < 0) {
	*info = -3;
    } else if (*ldb < max(1,*n)) {
	*info = -6;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("SPPSV ", &i__1);
	return 0;
    }

/*     Compute the Cholesky factorization A = U'*U or A = L*L'. */

    spptrf_(uplo, n, &ap[1], info);
    if (*info == 0) {

/*        Solve the system A*X = B, overwriting B with X. */

	spptrs_(uplo, n, nrhs, &ap[1], &b[b_offset], ldb, info);

    }
    return 0;

/*     End of SPPSV */

} /* sppsv_ */