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

/* Subroutine */ int sstevd_(char *jobz, integer *n, real *d__, real *e, real 
	*z__, integer *ldz, real *work, integer *lwork, integer *iwork, 
	integer *liwork, 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   
       June 30, 1999   


    Purpose   
    =======   

    SSTEVD computes all eigenvalues and, optionally, eigenvectors of a   
    real symmetric tridiagonal matrix. If eigenvectors are desired, it   
    uses a divide and conquer algorithm.   

    The divide and conquer algorithm makes very mild assumptions about   
    floating point arithmetic. It will work on machines with a guard   
    digit in add/subtract, or on those binary machines without guard   
    digits which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or   
    Cray-2. It could conceivably fail on hexadecimal or decimal machines   
    without guard digits, but we know of none.   

    Arguments   
    =========   

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

    N       (input) INTEGER   
            The order of the matrix.  N >= 0.   

    D       (input/output) REAL array, dimension (N)   
            On entry, the n diagonal elements of the tridiagonal matrix   
            A.   
            On exit, if INFO = 0, the eigenvalues in ascending order.   

    E       (input/output) REAL array, dimension (N)   
            On entry, the (n-1) subdiagonal elements of the tridiagonal   
            matrix A, stored in elements 1 to N-1 of E; E(N) need not   
            be set, but is used by the routine.   
            On exit, the contents of E are destroyed.   

    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 D(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/output) REAL array,   
                                           dimension (LWORK)   
            On exit, if INFO = 0, WORK(1) returns the optimal LWORK.   

    LWORK   (input) INTEGER   
            The dimension of the array WORK.   
            If JOBZ  = 'N' or N <= 1 then LWORK must be at least 1.   
            If JOBZ  = 'V' and N > 1 then LWORK must be at least   
                           ( 1 + 4*N + N**2 ).   

            If LWORK = -1, then a workspace query is assumed; the routine   
            only calculates the optimal size of the WORK array, returns   
            this value as the first entry of the WORK array, and no error   
            message related to LWORK is issued by XERBLA.   

    IWORK   (workspace/output) INTEGER array, dimension (LIWORK)   
            On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.   

    LIWORK  (input) INTEGER   
            The dimension of the array IWORK.   
            If JOBZ  = 'N' or N <= 1 then LIWORK must be at least 1.   
            If JOBZ  = 'V' and N > 1 then LIWORK must be at least 3+5*N.   

            If LIWORK = -1, then a workspace query is assumed; the   
            routine only calculates the optimal size of the IWORK array,   
            returns this value as the first entry of the IWORK array, and   
            no error message related to LIWORK is issued by XERBLA.   

    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 E 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 real rmin, rmax, tnrm, sigma;
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *);
    static integer lwmin;
    static logical wantz;
    static integer iscale;
    extern doublereal slamch_(char *);
    static real safmin;
    extern /* Subroutine */ int xerbla_(char *, integer *);
    static real bignum;
    extern /* Subroutine */ int sstedc_(char *, integer *, real *, real *, 
	    real *, integer *, real *, integer *, integer *, integer *, 
	    integer *);
    static integer liwmin;
    extern doublereal slanst_(char *, integer *, real *, real *);
    extern /* Subroutine */ int ssterf_(integer *, real *, real *, integer *);
    static real smlnum;
    static logical lquery;
    static real eps;
#define z___ref(a_1,a_2) z__[(a_2)*z_dim1 + a_1]


    --d__;
    --e;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1 * 1;
    z__ -= z_offset;
    --work;
    --iwork;

    /* Function Body */
    wantz = lsame_(jobz, "V");
    lquery = *lwork == -1 || *liwork == -1;

    *info = 0;
    liwmin = 1;
    lwmin = 1;
    if (*n > 1 && wantz) {
/* Computing 2nd power */
	i__1 = *n;
	lwmin = (*n << 2) + 1 + i__1 * i__1;
	liwmin = *n * 5 + 3;
    }

    if (! (wantz || lsame_(jobz, "N"))) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*ldz < 1 || wantz && *ldz < *n) {
	*info = -6;
    } else if (*lwork < lwmin && ! lquery) {
	*info = -8;
    } else if (*liwork < liwmin && ! lquery) {
	*info = -10;
    }

    if (*info == 0) {
	work[1] = (real) lwmin;
	iwork[1] = liwmin;
    }

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

/*     Quick return if possible */

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

    if (*n == 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. */

    iscale = 0;
    tnrm = slanst_("M", n, &d__[1], &e[1]);
    if (tnrm > 0.f && tnrm < rmin) {
	iscale = 1;
	sigma = rmin / tnrm;
    } else if (tnrm > rmax) {
	iscale = 1;
	sigma = rmax / tnrm;
    }
    if (iscale == 1) {
	sscal_(n, &sigma, &d__[1], &c__1);
	i__1 = *n - 1;
	sscal_(&i__1, &sigma, &e[1], &c__1);
    }

/*     For eigenvalues only, call SSTERF.  For eigenvalues and   
       eigenvectors, call SSTEDC. */

    if (! wantz) {
	ssterf_(n, &d__[1], &e[1], info);
    } else {
	sstedc_("I", n, &d__[1], &e[1], &z__[z_offset], ldz, &work[1], lwork, 
		&iwork[1], liwork, info);
    }

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

    if (iscale == 1) {
	r__1 = 1.f / sigma;
	sscal_(n, &r__1, &d__[1], &c__1);
    }

    work[1] = (real) lwmin;
    iwork[1] = liwmin;

    return 0;

/*     End of SSTEVD */

} /* sstevd_ */

#undef z___ref


