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

/* Subroutine */ int sspev_(char *jobz, char *uplo, integer *n, real *ap, 
	real *w, real *z__, integer *ldz, real *work, 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   
    =======   

    SSPEV computes all the eigenvalues and, optionally, eigenvectors of a   
    real symmetric matrix A in packed storage.   

    Arguments   
    =========   

    JOBZ    (input) CHARACTER*1   
            = 'N':  Compute eigenvalues only;   
            = 'V':  Compute eigenvalues and eigenvectors.   

    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.   

    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)*(2*n-j)/2) = A(i,j) for j<=i<=n.   

            On exit, AP is overwritten by values generated during the   
            reduction to tridiagonal form.  If UPLO = 'U', the diagonal   
            and first superdiagonal of the tridiagonal matrix T overwrite   
            the corresponding elements of A, and if UPLO = 'L', the   
            diagonal and first subdiagonal of T overwrite the   
            corresponding elements of A.   

    W       (output) REAL array, dimension (N)   
            If INFO = 0, the eigenvalues in ascending order.   

    Z       (output) REAL array, dimension (LDZ, N)   
            If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal   
            eigenvectors of the matrix A, with the i-th column of Z   
            holding the eigenvector associated with W(i).   
            If JOBZ = 'N', then Z is not referenced.   

    LDZ     (input) INTEGER   
            The leading dimension of the array Z.  LDZ >= 1, and if   
            JOBZ = 'V', LDZ >= max(1,N).   

    WORK    (workspace) REAL array, dimension (3*N)   

    INFO    (output) INTEGER   
            = 0:  successful exit.   
            < 0:  if INFO = -i, the i-th argument had an illegal value.   
            > 0:  if INFO = i, the algorithm failed to converge; i   
                  off-diagonal elements of an intermediate tridiagonal   
                  form did not converge to zero.   

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


       Test the input parameters.   

       Parameter adjustments */
    /* Table of constant values */
    static integer c__1 = 1;
    
    /* System generated locals */
    integer z_dim1, z_offset, i__1;
    real r__1;
    /* Builtin functions */
    double sqrt(doublereal);
    /* Local variables */
    static integer inde;
    static real anrm;
    static integer imax;
    static real rmin, rmax, sigma;
    extern logical lsame_(char *, char *);
    static integer iinfo;
    extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *);
    static logical wantz;
    static integer iscale;
    extern doublereal slamch_(char *);
    static real safmin;
    extern /* Subroutine */ int xerbla_(char *, integer *);
    static real bignum;
    static integer indtau, indwrk;
    extern doublereal slansp_(char *, char *, integer *, real *, real *);
    extern /* Subroutine */ int ssterf_(integer *, real *, real *, integer *);
    static real smlnum;
    extern /* Subroutine */ int sopgtr_(char *, integer *, real *, real *, 
	    real *, integer *, real *, integer *), ssptrd_(char *, 
	    integer *, real *, real *, real *, real *, integer *), 
	    ssteqr_(char *, integer *, real *, real *, real *, integer *, 
	    real *, integer *);
    static real eps;
#define z___ref(a_1,a_2) z__[(a_2)*z_dim1 + a_1]


    --ap;
    --w;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1 * 1;
    z__ -= z_offset;
    --work;

    /* Function Body */
    wantz = lsame_(jobz, "V");

    *info = 0;
    if (! (wantz || lsame_(jobz, "N"))) {
	*info = -1;
    } else if (! (lsame_(uplo, "U") || lsame_(uplo, 
	    "L"))) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*ldz < 1 || wantz && *ldz < *n) {
	*info = -7;
    }

    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("SSPEV ", &i__1);
	return 0;
    }

/*     Quick return if possible */

    if (*n == 0) {
	return 0;
    }

    if (*n == 1) {
	w[1] = ap[1];
	if (wantz) {
	    z___ref(1, 1) = 1.f;
	}
	return 0;
    }

/*     Get machine constants. */

    safmin = slamch_("Safe minimum");
    eps = slamch_("Precision");
    smlnum = safmin / eps;
    bignum = 1.f / smlnum;
    rmin = sqrt(smlnum);
    rmax = sqrt(bignum);

/*     Scale matrix to allowable range, if necessary. */

    anrm = slansp_("M", uplo, n, &ap[1], &work[1]);
    iscale = 0;
    if (anrm > 0.f && anrm < rmin) {
	iscale = 1;
	sigma = rmin / anrm;
    } else if (anrm > rmax) {
	iscale = 1;
	sigma = rmax / anrm;
    }
    if (iscale == 1) {
	i__1 = *n * (*n + 1) / 2;
	sscal_(&i__1, &sigma, &ap[1], &c__1);
    }

/*     Call SSPTRD to reduce symmetric packed matrix to tridiagonal form. */

    inde = 1;
    indtau = inde + *n;
    ssptrd_(uplo, n, &ap[1], &w[1], &work[inde], &work[indtau], &iinfo);

/*     For eigenvalues only, call SSTERF.  For eigenvectors, first call   
       SOPGTR to generate the orthogonal matrix, then call SSTEQR. */

    if (! wantz) {
	ssterf_(n, &w[1], &work[inde], info);
    } else {
	indwrk = indtau + *n;
	sopgtr_(uplo, n, &ap[1], &work[indtau], &z__[z_offset], ldz, &work[
		indwrk], &iinfo);
	ssteqr_(jobz, n, &w[1], &work[inde], &z__[z_offset], ldz, &work[
		indtau], info);
    }

/*     If matrix was scaled, then rescale eigenvalues appropriately. */

    if (iscale == 1) {
	if (*info == 0) {
	    imax = *n;
	} else {
	    imax = *info - 1;
	}
	r__1 = 1.f / sigma;
	sscal_(&imax, &r__1, &w[1], &c__1);
    }

    return 0;

/*     End of SSPEV */

} /* sspev_ */

#undef z___ref


