/*  -- translated by f2c (version 20191129).
   You must link the resulting object file with libf2c:
	on Microsoft Windows system, link with libf2c.lib;
	on Linux or Unix systems, link with .../path/to/libf2c.a -lm
	or, if you install libf2c.a in a standard place, with -lf2c -lm
	-- in that order, at the end of the command line, as in
		cc *.o -lf2c -lm
	Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,

		http://www.netlib.org/f2c/libf2c.zip
*/

#include "f2c.h"

/* Table of constant values */

static integer c__10 = 10;
static integer c__1 = 1;
static integer c__2 = 2;
static integer c__3 = 3;
static integer c__4 = 4;
static integer c_n1 = -1;

/* > \brief <b> DSYEVR computes the eigenvalues and, optionally, the left and/or right eigenvectors for SY mat
rices</b>   

    =========== DOCUMENTATION ===========   

   Online html documentation available at   
              http://www.netlib.org/lapack/explore-html/   

   > \htmlonly   
   > Download DSYEVR + dependencies   
   > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dsyevr.
f">   
   > [TGZ]</a>   
   > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dsyevr.
f">   
   > [ZIP]</a>   
   > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dsyevr.
f">   
   > [TXT]</a>   
   > \endhtmlonly   

    Definition:   
    ===========   

         SUBROUTINE DSYEVR( JOBZ, RANGE, UPLO, N, A, LDA, VL, VU, IL, IU,   
                            ABSTOL, M, W, Z, LDZ, ISUPPZ, WORK, LWORK,   
                            IWORK, LIWORK, INFO )   

         CHARACTER          JOBZ, RANGE, UPLO   
         INTEGER            IL, INFO, IU, LDA, LDZ, LIWORK, LWORK, M, N   
         DOUBLE PRECISION   ABSTOL, VL, VU   
         INTEGER            ISUPPZ( * ), IWORK( * )   
         DOUBLE PRECISION   A( LDA, * ), W( * ), WORK( * ), Z( LDZ, * )   


   > \par Purpose:   
    =============   
   >   
   > \verbatim   
   >   
   > DSYEVR computes selected eigenvalues and, optionally, eigenvectors   
   > of a real symmetric matrix A.  Eigenvalues and eigenvectors can be   
   > selected by specifying either a range of values or a range of   
   > indices for the desired eigenvalues.   
   >   
   > DSYEVR first reduces the matrix A to tridiagonal form T with a call   
   > to DSYTRD.  Then, whenever possible, DSYEVR calls DSTEMR to compute   
   > the eigenspectrum using Relatively Robust Representations.  DSTEMR   
   > computes eigenvalues by the dqds algorithm, while orthogonal   
   > eigenvectors are computed from various "good" L D L^T representations   
   > (also known as Relatively Robust Representations). Gram-Schmidt   
   > orthogonalization is avoided as far as possible. More specifically,   
   > the various steps of the algorithm are as follows.   
   >   
   > For each unreduced block (submatrix) of T,   
   >    (a) Compute T - sigma I  = L D L^T, so that L and D   
   >        define all the wanted eigenvalues to high relative accuracy.   
   >        This means that small relative changes in the entries of D and L   
   >        cause only small relative changes in the eigenvalues and   
   >        eigenvectors. The standard (unfactored) representation of the   
   >        tridiagonal matrix T does not have this property in general.   
   >    (b) Compute the eigenvalues to suitable accuracy.   
   >        If the eigenvectors are desired, the algorithm attains full   
   >        accuracy of the computed eigenvalues only right before   
   >        the corresponding vectors have to be computed, see steps c) and d).   
   >    (c) For each cluster of close eigenvalues, select a new   
   >        shift close to the cluster, find a new factorization, and refine   
   >        the shifted eigenvalues to suitable accuracy.   
   >    (d) For each eigenvalue with a large enough relative separation compute   
   >        the corresponding eigenvector by forming a rank revealing twisted   
   >        factorization. Go back to (c) for any clusters that remain.   
   >   
   > The desired accuracy of the output can be specified by the input   
   > parameter ABSTOL.   
   >   
   > For more details, see DSTEMR's documentation and:   
   > - Inderjit S. Dhillon and Beresford N. Parlett: "Multiple representations   
   >   to compute orthogonal eigenvectors of symmetric tridiagonal matrices,"   
   >   Linear Algebra and its Applications, 387(1), pp. 1-28, August 2004.   
   > - Inderjit Dhillon and Beresford Parlett: "Orthogonal Eigenvectors and   
   >   Relative Gaps," SIAM Journal on Matrix Analysis and Applications, Vol. 25,   
   >   2004.  Also LAPACK Working Note 154.   
   > - Inderjit Dhillon: "A new O(n^2) algorithm for the symmetric   
   >   tridiagonal eigenvalue/eigenvector problem",   
   >   Computer Science Division Technical Report No. UCB/CSD-97-971,   
   >   UC Berkeley, May 1997.   
   >   
   >   
   > Note 1 : DSYEVR calls DSTEMR when the full spectrum is requested   
   > on machines which conform to the ieee-754 floating point standard.   
   > DSYEVR calls DSTEBZ and SSTEIN on non-ieee machines and   
   > when partial spectrum requests are made.   
   >   
   > Normal execution of DSTEMR may create NaNs and infinities and   
   > hence may abort due to a floating point exception in environments   
   > which do not handle NaNs and infinities in the ieee standard default   
   > manner.   
   > \endverbatim   

    Arguments:   
    ==========   

   > \param[in] JOBZ   
   > \verbatim   
   >          JOBZ is CHARACTER*1   
   >          = 'N':  Compute eigenvalues only;   
   >          = 'V':  Compute eigenvalues and eigenvectors.   
   > \endverbatim   
   >   
   > \param[in] RANGE   
   > \verbatim   
   >          RANGE is CHARACTER*1   
   >          = 'A': all eigenvalues will be found.   
   >          = 'V': all eigenvalues in the half-open interval (VL,VU]   
   >                 will be found.   
   >          = 'I': the IL-th through IU-th eigenvalues will be found.   
   >          For RANGE = 'V' or 'I' and IU - IL < N - 1, DSTEBZ and   
   >          DSTEIN are called   
   > \endverbatim   
   >   
   > \param[in] UPLO   
   > \verbatim   
   >          UPLO is CHARACTER*1   
   >          = 'U':  Upper triangle of A is stored;   
   >          = 'L':  Lower triangle of A is stored.   
   > \endverbatim   
   >   
   > \param[in] N   
   > \verbatim   
   >          N is INTEGER   
   >          The order of the matrix A.  N >= 0.   
   > \endverbatim   
   >   
   > \param[in,out] A   
   > \verbatim   
   >          A is DOUBLE PRECISION array, dimension (LDA, N)   
   >          On entry, the symmetric matrix A.  If UPLO = 'U', the   
   >          leading N-by-N upper triangular part of A contains the   
   >          upper triangular part of the matrix A.  If UPLO = 'L',   
   >          the leading N-by-N lower triangular part of A contains   
   >          the lower triangular part of the matrix A.   
   >          On exit, the lower triangle (if UPLO='L') or the upper   
   >          triangle (if UPLO='U') of A, including the diagonal, is   
   >          destroyed.   
   > \endverbatim   
   >   
   > \param[in] LDA   
   > \verbatim   
   >          LDA is INTEGER   
   >          The leading dimension of the array A.  LDA >= max(1,N).   
   > \endverbatim   
   >   
   > \param[in] VL   
   > \verbatim   
   >          VL is DOUBLE PRECISION   
   > \endverbatim   
   >   
   > \param[in] VU   
   > \verbatim   
   >          VU is DOUBLE PRECISION   
   >          If RANGE='V', the lower and upper bounds of the interval to   
   >          be searched for eigenvalues. VL < VU.   
   >          Not referenced if RANGE = 'A' or 'I'.   
   > \endverbatim   
   >   
   > \param[in] IL   
   > \verbatim   
   >          IL is INTEGER   
   > \endverbatim   
   >   
   > \param[in] IU   
   > \verbatim   
   >          IU is INTEGER   
   >          If RANGE='I', the indices (in ascending order) of the   
   >          smallest and largest eigenvalues to be returned.   
   >          1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0.   
   >          Not referenced if RANGE = 'A' or 'V'.   
   > \endverbatim   
   >   
   > \param[in] ABSTOL   
   > \verbatim   
   >          ABSTOL is DOUBLE PRECISION   
   >          The absolute error tolerance for the eigenvalues.   
   >          An approximate eigenvalue is accepted as converged   
   >          when it is determined to lie in an interval [a,b]   
   >          of width less than or equal to   
   >   
   >                  ABSTOL + EPS *   max( |a|,|b| ) ,   
   >   
   >          where EPS is the machine precision.  If ABSTOL is less than   
   >          or equal to zero, then  EPS*|T|  will be used in its place,   
   >          where |T| is the 1-norm of the tridiagonal matrix obtained   
   >          by reducing A to tridiagonal form.   
   >   
   >          See "Computing Small Singular Values of Bidiagonal Matrices   
   >          with Guaranteed High Relative Accuracy," by Demmel and   
   >          Kahan, LAPACK Working Note #3.   
   >   
   >          If high relative accuracy is important, set ABSTOL to   
   >          DLAMCH( 'Safe minimum' ).  Doing so will guarantee that   
   >          eigenvalues are computed to high relative accuracy when   
   >          possible in future releases.  The current code does not   
   >          make any guarantees about high relative accuracy, but   
   >          future releases will. See J. Barlow and J. Demmel,   
   >          "Computing Accurate Eigensystems of Scaled Diagonally   
   >          Dominant Matrices", LAPACK Working Note #7, for a discussion   
   >          of which matrices define their eigenvalues to high relative   
   >          accuracy.   
   > \endverbatim   
   >   
   > \param[out] M   
   > \verbatim   
   >          M is INTEGER   
   >          The total number of eigenvalues found.  0 <= M <= N.   
   >          If RANGE = 'A', M = N, and if RANGE = 'I', M = IU-IL+1.   
   > \endverbatim   
   >   
   > \param[out] W   
   > \verbatim   
   >          W is DOUBLE PRECISION array, dimension (N)   
   >          The first M elements contain the selected eigenvalues in   
   >          ascending order.   
   > \endverbatim   
   >   
   > \param[out] Z   
   > \verbatim   
   >          Z is DOUBLE PRECISION array, dimension (LDZ, max(1,M))   
   >          If JOBZ = 'V', then if INFO = 0, the first M columns of Z   
   >          contain the orthonormal eigenvectors of the matrix A   
   >          corresponding to the selected eigenvalues, with the i-th   
   >          column of Z holding the eigenvector associated with W(i).   
   >          If JOBZ = 'N', then Z is not referenced.   
   >          Note: the user must ensure that at least max(1,M) columns are   
   >          supplied in the array Z; if RANGE = 'V', the exact value of M   
   >          is not known in advance and an upper bound must be used.   
   >          Supplying N columns is always safe.   
   > \endverbatim   
   >   
   > \param[in] LDZ   
   > \verbatim   
   >          LDZ is INTEGER   
   >          The leading dimension of the array Z.  LDZ >= 1, and if   
   >          JOBZ = 'V', LDZ >= max(1,N).   
   > \endverbatim   
   >   
   > \param[out] ISUPPZ   
   > \verbatim   
   >          ISUPPZ is INTEGER array, dimension ( 2*max(1,M) )   
   >          The support of the eigenvectors in Z, i.e., the indices   
   >          indicating the nonzero elements in Z. The i-th eigenvector   
   >          is nonzero only in elements ISUPPZ( 2*i-1 ) through   
   >          ISUPPZ( 2*i ).   
   >          Implemented only for RANGE = 'A' or 'I' and IU - IL = N - 1   
   > \endverbatim   
   >   
   > \param[out] WORK   
   > \verbatim   
   >          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))   
   >          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.   
   > \endverbatim   
   >   
   > \param[in] LWORK   
   > \verbatim   
   >          LWORK is INTEGER   
   >          The dimension of the array WORK.  LWORK >= max(1,26*N).   
   >          For optimal efficiency, LWORK >= (NB+6)*N,   
   >          where NB is the max of the blocksize for DSYTRD and DORMTR   
   >          returned by ILAENV.   
   >   
   >          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.   
   > \endverbatim   
   >   
   > \param[out] IWORK   
   > \verbatim   
   >          IWORK is INTEGER array, dimension (MAX(1,LIWORK))   
   >          On exit, if INFO = 0, IWORK(1) returns the optimal LWORK.   
   > \endverbatim   
   >   
   > \param[in] LIWORK   
   > \verbatim   
   >          LIWORK is INTEGER   
   >          The dimension of the array IWORK.  LIWORK >= max(1,10*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.   
   > \endverbatim   
   >   
   > \param[out] INFO   
   > \verbatim   
   >          INFO is INTEGER   
   >          = 0:  successful exit   
   >          < 0:  if INFO = -i, the i-th argument had an illegal value   
   >          > 0:  Internal error   
   > \endverbatim   

    Authors:   
    ========   

   > \author Univ. of Tennessee   
   > \author Univ. of California Berkeley   
   > \author Univ. of Colorado Denver   
   > \author NAG Ltd.   

   > \date September 2012   

   > \ingroup doubleSYeigen   

   > \par Contributors:   
    ==================   
   >   
   >     Inderjit Dhillon, IBM Almaden, USA \n   
   >     Osni Marques, LBNL/NERSC, USA \n   
   >     Ken Stanley, Computer Science Division, University of   
   >       California at Berkeley, USA \n   
   >     Jason Riedy, Computer Science Division, University of   
   >       California at Berkeley, USA \n   
   >   
    =====================================================================   
   Subroutine */ int igraphdsyevr_(char *jobz, char *range, char *uplo, integer *n, 
	doublereal *a, integer *lda, doublereal *vl, doublereal *vu, integer *
	il, integer *iu, doublereal *abstol, integer *m, doublereal *w, 
	doublereal *z__, integer *ldz, integer *isuppz, doublereal *work, 
	integer *lwork, integer *iwork, integer *liwork, integer *info)
{
    /* System generated locals */
    integer a_dim1, a_offset, z_dim1, z_offset, i__1, i__2;
    doublereal d__1, d__2;

    /* Builtin functions */
    double sqrt(doublereal);

    /* Local variables */
    integer i__, j, nb, jj;
    doublereal eps, vll, vuu, tmp1;
    integer indd, inde;
    doublereal anrm;
    integer imax;
    doublereal rmin, rmax;
    integer inddd, indee;
    extern /* Subroutine */ int igraphdscal_(integer *, doublereal *, doublereal *, 
	    integer *);
    doublereal sigma;
    extern logical igraphlsame_(char *, char *);
    integer iinfo;
    char order[1];
    integer indwk;
    extern /* Subroutine */ int igraphdcopy_(integer *, doublereal *, integer *, 
	    doublereal *, integer *), igraphdswap_(integer *, doublereal *, integer 
	    *, doublereal *, integer *);
    integer lwmin;
    logical lower, wantz;
    extern doublereal igraphdlamch_(char *);
    logical alleig, indeig;
    integer iscale, ieeeok, indibl, indifl;
    logical valeig;
    doublereal safmin;
    extern integer igraphilaenv_(integer *, char *, char *, integer *, integer *, 
	    integer *, integer *, ftnlen, ftnlen);
    extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);
    doublereal abstll, bignum;
    integer indtau, indisp;
    extern /* Subroutine */ int igraphdstein_(integer *, doublereal *, doublereal *,
	     integer *, doublereal *, integer *, integer *, doublereal *, 
	    integer *, doublereal *, integer *, integer *, integer *), 
	    igraphdsterf_(integer *, doublereal *, doublereal *, integer *);
    integer indiwo, indwkn;
    extern doublereal igraphdlansy_(char *, char *, integer *, doublereal *, 
	    integer *, doublereal *);
    extern /* Subroutine */ int igraphdstebz_(char *, char *, integer *, doublereal 
	    *, doublereal *, integer *, integer *, doublereal *, doublereal *,
	     doublereal *, integer *, integer *, doublereal *, integer *, 
	    integer *, doublereal *, integer *, integer *), 
	    igraphdstemr_(char *, char *, integer *, doublereal *, doublereal *, 
	    doublereal *, doublereal *, integer *, integer *, integer *, 
	    doublereal *, doublereal *, integer *, integer *, integer *, 
	    logical *, doublereal *, integer *, integer *, integer *, integer 
	    *);
    integer liwmin;
    logical tryrac;
    extern /* Subroutine */ int igraphdormtr_(char *, char *, char *, integer *, 
	    integer *, doublereal *, integer *, doublereal *, doublereal *, 
	    integer *, doublereal *, integer *, integer *);
    integer llwrkn, llwork, nsplit;
    doublereal smlnum;
    extern /* Subroutine */ int igraphdsytrd_(char *, integer *, doublereal *, 
	    integer *, doublereal *, doublereal *, doublereal *, doublereal *,
	     integer *, integer *);
    integer lwkopt;
    logical lquery;


/*  -- LAPACK driver routine (version 3.4.2) --   
    -- LAPACK is a software package provided by Univ. of Tennessee,    --   
    -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--   
       September 2012   


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


       Test the input parameters.   

       Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    --w;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1;
    z__ -= z_offset;
    --isuppz;
    --work;
    --iwork;

    /* Function Body */
    ieeeok = igraphilaenv_(&c__10, "DSYEVR", "N", &c__1, &c__2, &c__3, &c__4, (
	    ftnlen)6, (ftnlen)1);

    lower = igraphlsame_(uplo, "L");
    wantz = igraphlsame_(jobz, "V");
    alleig = igraphlsame_(range, "A");
    valeig = igraphlsame_(range, "V");
    indeig = igraphlsame_(range, "I");

    lquery = *lwork == -1 || *liwork == -1;

/* Computing MAX */
    i__1 = 1, i__2 = *n * 26;
    lwmin = max(i__1,i__2);
/* Computing MAX */
    i__1 = 1, i__2 = *n * 10;
    liwmin = max(i__1,i__2);

    *info = 0;
    if (! (wantz || igraphlsame_(jobz, "N"))) {
	*info = -1;
    } else if (! (alleig || valeig || indeig)) {
	*info = -2;
    } else if (! (lower || igraphlsame_(uplo, "U"))) {
	*info = -3;
    } else if (*n < 0) {
	*info = -4;
    } else if (*lda < max(1,*n)) {
	*info = -6;
    } else {
	if (valeig) {
	    if (*n > 0 && *vu <= *vl) {
		*info = -8;
	    }
	} else if (indeig) {
	    if (*il < 1 || *il > max(1,*n)) {
		*info = -9;
	    } else if (*iu < min(*n,*il) || *iu > *n) {
		*info = -10;
	    }
	}
    }
    if (*info == 0) {
	if (*ldz < 1 || wantz && *ldz < *n) {
	    *info = -15;
	} else if (*lwork < lwmin && ! lquery) {
	    *info = -18;
	} else if (*liwork < liwmin && ! lquery) {
	    *info = -20;
	}
    }

    if (*info == 0) {
	nb = igraphilaenv_(&c__1, "DSYTRD", uplo, n, &c_n1, &c_n1, &c_n1, (ftnlen)6,
		 (ftnlen)1);
/* Computing MAX */
	i__1 = nb, i__2 = igraphilaenv_(&c__1, "DORMTR", uplo, n, &c_n1, &c_n1, &
		c_n1, (ftnlen)6, (ftnlen)1);
	nb = max(i__1,i__2);
/* Computing MAX */
	i__1 = (nb + 1) * *n;
	lwkopt = max(i__1,lwmin);
	work[1] = (doublereal) lwkopt;
	iwork[1] = liwmin;
    }

    if (*info != 0) {
	i__1 = -(*info);
	igraphxerbla_("DSYEVR", &i__1, (ftnlen)6);
	return 0;
    } else if (lquery) {
	return 0;
    }

/*     Quick return if possible */

    *m = 0;
    if (*n == 0) {
	work[1] = 1.;
	return 0;
    }

    if (*n == 1) {
	work[1] = 7.;
	if (alleig || indeig) {
	    *m = 1;
	    w[1] = a[a_dim1 + 1];
	} else {
	    if (*vl < a[a_dim1 + 1] && *vu >= a[a_dim1 + 1]) {
		*m = 1;
		w[1] = a[a_dim1 + 1];
	    }
	}
	if (wantz) {
	    z__[z_dim1 + 1] = 1.;
	    isuppz[1] = 1;
	    isuppz[2] = 1;
	}
	return 0;
    }

/*     Get machine constants. */

    safmin = igraphdlamch_("Safe minimum");
    eps = igraphdlamch_("Precision");
    smlnum = safmin / eps;
    bignum = 1. / smlnum;
    rmin = sqrt(smlnum);
/* Computing MIN */
    d__1 = sqrt(bignum), d__2 = 1. / sqrt(sqrt(safmin));
    rmax = min(d__1,d__2);

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

    iscale = 0;
    abstll = *abstol;
    if (valeig) {
	vll = *vl;
	vuu = *vu;
    }
    anrm = igraphdlansy_("M", uplo, n, &a[a_offset], lda, &work[1]);
    if (anrm > 0. && anrm < rmin) {
	iscale = 1;
	sigma = rmin / anrm;
    } else if (anrm > rmax) {
	iscale = 1;
	sigma = rmax / anrm;
    }
    if (iscale == 1) {
	if (lower) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__2 = *n - j + 1;
		igraphdscal_(&i__2, &sigma, &a[j + j * a_dim1], &c__1);
/* L10: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		igraphdscal_(&j, &sigma, &a[j * a_dim1 + 1], &c__1);
/* L20: */
	    }
	}
	if (*abstol > 0.) {
	    abstll = *abstol * sigma;
	}
	if (valeig) {
	    vll = *vl * sigma;
	    vuu = *vu * sigma;
	}
    }
/*     Initialize indices into workspaces.  Note: The IWORK indices are   
       used only if DSTERF or DSTEMR fail.   
       WORK(INDTAU:INDTAU+N-1) stores the scalar factors of the   
       elementary reflectors used in DSYTRD. */
    indtau = 1;
/*     WORK(INDD:INDD+N-1) stores the tridiagonal's diagonal entries. */
    indd = indtau + *n;
/*     WORK(INDE:INDE+N-1) stores the off-diagonal entries of the   
       tridiagonal matrix from DSYTRD. */
    inde = indd + *n;
/*     WORK(INDDD:INDDD+N-1) is a copy of the diagonal entries over   
       -written by DSTEMR (the DSTERF path copies the diagonal to W). */
    inddd = inde + *n;
/*     WORK(INDEE:INDEE+N-1) is a copy of the off-diagonal entries over   
       -written while computing the eigenvalues in DSTERF and DSTEMR. */
    indee = inddd + *n;
/*     INDWK is the starting offset of the left-over workspace, and   
       LLWORK is the remaining workspace size. */
    indwk = indee + *n;
    llwork = *lwork - indwk + 1;
/*     IWORK(INDIBL:INDIBL+M-1) corresponds to IBLOCK in DSTEBZ and   
       stores the block indices of each of the M<=N eigenvalues. */
    indibl = 1;
/*     IWORK(INDISP:INDISP+NSPLIT-1) corresponds to ISPLIT in DSTEBZ and   
       stores the starting and finishing indices of each block. */
    indisp = indibl + *n;
/*     IWORK(INDIFL:INDIFL+N-1) stores the indices of eigenvectors   
       that corresponding to eigenvectors that fail to converge in   
       DSTEIN.  This information is discarded; if any fail, the driver   
       returns INFO > 0. */
    indifl = indisp + *n;
/*     INDIWO is the offset of the remaining integer workspace. */
    indiwo = indifl + *n;

/*     Call DSYTRD to reduce symmetric matrix to tridiagonal form. */

    igraphdsytrd_(uplo, n, &a[a_offset], lda, &work[indd], &work[inde], &work[
	    indtau], &work[indwk], &llwork, &iinfo);

/*     If all eigenvalues are desired   
       then call DSTERF or DSTEMR and DORMTR. */

    if ((alleig || indeig && *il == 1 && *iu == *n) && ieeeok == 1) {
	if (! wantz) {
	    igraphdcopy_(n, &work[indd], &c__1, &w[1], &c__1);
	    i__1 = *n - 1;
	    igraphdcopy_(&i__1, &work[inde], &c__1, &work[indee], &c__1);
	    igraphdsterf_(n, &w[1], &work[indee], info);
	} else {
	    i__1 = *n - 1;
	    igraphdcopy_(&i__1, &work[inde], &c__1, &work[indee], &c__1);
	    igraphdcopy_(n, &work[indd], &c__1, &work[inddd], &c__1);

	    if (*abstol <= *n * 2. * eps) {
		tryrac = TRUE_;
	    } else {
		tryrac = FALSE_;
	    }
	    igraphdstemr_(jobz, "A", n, &work[inddd], &work[indee], vl, vu, il, iu, 
		    m, &w[1], &z__[z_offset], ldz, n, &isuppz[1], &tryrac, &
		    work[indwk], lwork, &iwork[1], liwork, info);



/*        Apply orthogonal matrix used in reduction to tridiagonal   
          form to eigenvectors returned by DSTEIN. */

	    if (wantz && *info == 0) {
		indwkn = inde;
		llwrkn = *lwork - indwkn + 1;
		igraphdormtr_("L", uplo, "N", n, m, &a[a_offset], lda, &work[indtau]
			, &z__[z_offset], ldz, &work[indwkn], &llwrkn, &iinfo);
	    }
	}


	if (*info == 0) {
/*           Everything worked.  Skip DSTEBZ/DSTEIN.  IWORK(:) are   
             undefined. */
	    *m = *n;
	    goto L30;
	}
	*info = 0;
    }

/*     Otherwise, call DSTEBZ and, if eigenvectors are desired, DSTEIN.   
       Also call DSTEBZ and DSTEIN if DSTEMR fails. */

    if (wantz) {
	*(unsigned char *)order = 'B';
    } else {
	*(unsigned char *)order = 'E';
    }
    igraphdstebz_(range, order, n, &vll, &vuu, il, iu, &abstll, &work[indd], &work[
	    inde], m, &nsplit, &w[1], &iwork[indibl], &iwork[indisp], &work[
	    indwk], &iwork[indiwo], info);

    if (wantz) {
	igraphdstein_(n, &work[indd], &work[inde], m, &w[1], &iwork[indibl], &iwork[
		indisp], &z__[z_offset], ldz, &work[indwk], &iwork[indiwo], &
		iwork[indifl], info);

/*        Apply orthogonal matrix used in reduction to tridiagonal   
          form to eigenvectors returned by DSTEIN. */

	indwkn = inde;
	llwrkn = *lwork - indwkn + 1;
	igraphdormtr_("L", uplo, "N", n, m, &a[a_offset], lda, &work[indtau], &z__[
		z_offset], ldz, &work[indwkn], &llwrkn, &iinfo);
    }

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

    Jump here if DSTEMR/DSTEIN succeeded. */
L30:
    if (iscale == 1) {
	if (*info == 0) {
	    imax = *m;
	} else {
	    imax = *info - 1;
	}
	d__1 = 1. / sigma;
	igraphdscal_(&imax, &d__1, &w[1], &c__1);
    }

/*     If eigenvalues are not in order, then sort them, along with   
       eigenvectors.  Note: We do not sort the IFAIL portion of IWORK.   
       It may not be initialized (if DSTEMR/DSTEIN succeeded), and we do   
       not return this detailed information to the user. */

    if (wantz) {
	i__1 = *m - 1;
	for (j = 1; j <= i__1; ++j) {
	    i__ = 0;
	    tmp1 = w[j];
	    i__2 = *m;
	    for (jj = j + 1; jj <= i__2; ++jj) {
		if (w[jj] < tmp1) {
		    i__ = jj;
		    tmp1 = w[jj];
		}
/* L40: */
	    }

	    if (i__ != 0) {
		w[i__] = w[j];
		w[j] = tmp1;
		igraphdswap_(n, &z__[i__ * z_dim1 + 1], &c__1, &z__[j * z_dim1 + 1],
			 &c__1);
	    }
/* L50: */
	}
    }

/*     Set WORK(1) to optimal workspace size. */

    work[1] = (doublereal) lwkopt;
    iwork[1] = liwmin;

    return 0;

/*     End of DSYEVR */

} /* igraphdsyevr_ */