/*  -- translated by f2c (version 20100827).
   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__1 = 1;
static integer c_n1 = -1;
static integer c__3 = 3;
static integer c__2 = 2;
static integer c__0 = 0;

/* > \brief \b DLARRD computes the eigenvalues of a symmetric tridiagonal matrix to suitable accuracy.   

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

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

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

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

         SUBROUTINE DLARRD( RANGE, ORDER, N, VL, VU, IL, IU, GERS,   
                             RELTOL, D, E, E2, PIVMIN, NSPLIT, ISPLIT,   
                             M, W, WERR, WL, WU, IBLOCK, INDEXW,   
                             WORK, IWORK, INFO )   

         CHARACTER          ORDER, RANGE   
         INTEGER            IL, INFO, IU, M, N, NSPLIT   
         DOUBLE PRECISION    PIVMIN, RELTOL, VL, VU, WL, WU   
         INTEGER            IBLOCK( * ), INDEXW( * ),   
        $                   ISPLIT( * ), IWORK( * )   
         DOUBLE PRECISION   D( * ), E( * ), E2( * ),   
        $                   GERS( * ), W( * ), WERR( * ), WORK( * )   


   > \par Purpose:   
    =============   
   >   
   > \verbatim   
   >   
   > DLARRD computes the eigenvalues of a symmetric tridiagonal   
   > matrix T to suitable accuracy. This is an auxiliary code to be   
   > called from DSTEMR.   
   > The user may ask for all eigenvalues, all eigenvalues   
   > in the half-open interval (VL, VU], or the IL-th through IU-th   
   > eigenvalues.   
   >   
   > To avoid overflow, the matrix must be scaled so that its   
   > largest element is no greater than overflow**(1/2) * underflow**(1/4) in absolute value, and for greatest
   
   > accuracy, it should not be much smaller than that.   
   >   
   > See W. Kahan "Accurate Eigenvalues of a Symmetric Tridiagonal   
   > Matrix", Report CS41, Computer Science Dept., Stanford   
   > University, July 21, 1966.   
   > \endverbatim   

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

   > \param[in] RANGE   
   > \verbatim   
   >          RANGE is CHARACTER*1   
   >          = 'A': ("All")   all eigenvalues will be found.   
   >          = 'V': ("Value") all eigenvalues in the half-open interval   
   >                           (VL, VU] will be found.   
   >          = 'I': ("Index") the IL-th through IU-th eigenvalues (of the   
   >                           entire matrix) will be found.   
   > \endverbatim   
   >   
   > \param[in] ORDER   
   > \verbatim   
   >          ORDER is CHARACTER*1   
   >          = 'B': ("By Block") the eigenvalues will be grouped by   
   >                              split-off block (see IBLOCK, ISPLIT) and   
   >                              ordered from smallest to largest within   
   >                              the block.   
   >          = 'E': ("Entire matrix")   
   >                              the eigenvalues for the entire matrix   
   >                              will be ordered from smallest to   
   >                              largest.   
   > \endverbatim   
   >   
   > \param[in] N   
   > \verbatim   
   >          N is INTEGER   
   >          The order of the tridiagonal matrix T.  N >= 0.   
   > \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.  Eigenvalues less than or equal   
   >          to VL, or greater than VU, will not be returned.  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] GERS   
   > \verbatim   
   >          GERS is DOUBLE PRECISION array, dimension (2*N)   
   >          The N Gerschgorin intervals (the i-th Gerschgorin interval   
   >          is (GERS(2*i-1), GERS(2*i)).   
   > \endverbatim   
   >   
   > \param[in] RELTOL   
   > \verbatim   
   >          RELTOL is DOUBLE PRECISION   
   >          The minimum relative width of an interval.  When an interval   
   >          is narrower than RELTOL times the larger (in   
   >          magnitude) endpoint, then it is considered to be   
   >          sufficiently small, i.e., converged.  Note: this should   
   >          always be at least radix*machine epsilon.   
   > \endverbatim   
   >   
   > \param[in] D   
   > \verbatim   
   >          D is DOUBLE PRECISION array, dimension (N)   
   >          The n diagonal elements of the tridiagonal matrix T.   
   > \endverbatim   
   >   
   > \param[in] E   
   > \verbatim   
   >          E is DOUBLE PRECISION array, dimension (N-1)   
   >          The (n-1) off-diagonal elements of the tridiagonal matrix T.   
   > \endverbatim   
   >   
   > \param[in] E2   
   > \verbatim   
   >          E2 is DOUBLE PRECISION array, dimension (N-1)   
   >          The (n-1) squared off-diagonal elements of the tridiagonal matrix T.   
   > \endverbatim   
   >   
   > \param[in] PIVMIN   
   > \verbatim   
   >          PIVMIN is DOUBLE PRECISION   
   >          The minimum pivot allowed in the Sturm sequence for T.   
   > \endverbatim   
   >   
   > \param[in] NSPLIT   
   > \verbatim   
   >          NSPLIT is INTEGER   
   >          The number of diagonal blocks in the matrix T.   
   >          1 <= NSPLIT <= N.   
   > \endverbatim   
   >   
   > \param[in] ISPLIT   
   > \verbatim   
   >          ISPLIT is INTEGER array, dimension (N)   
   >          The splitting points, at which T breaks up into submatrices.   
   >          The first submatrix consists of rows/columns 1 to ISPLIT(1),   
   >          the second of rows/columns ISPLIT(1)+1 through ISPLIT(2),   
   >          etc., and the NSPLIT-th consists of rows/columns   
   >          ISPLIT(NSPLIT-1)+1 through ISPLIT(NSPLIT)=N.   
   >          (Only the first NSPLIT elements will actually be used, but   
   >          since the user cannot know a priori what value NSPLIT will   
   >          have, N words must be reserved for ISPLIT.)   
   > \endverbatim   
   >   
   > \param[out] M   
   > \verbatim   
   >          M is INTEGER   
   >          The actual number of eigenvalues found. 0 <= M <= N.   
   >          (See also the description of INFO=2,3.)   
   > \endverbatim   
   >   
   > \param[out] W   
   > \verbatim   
   >          W is DOUBLE PRECISION array, dimension (N)   
   >          On exit, the first M elements of W will contain the   
   >          eigenvalue approximations. DLARRD computes an interval   
   >          I_j = (a_j, b_j] that includes eigenvalue j. The eigenvalue   
   >          approximation is given as the interval midpoint   
   >          W(j)= ( a_j + b_j)/2. The corresponding error is bounded by   
   >          WERR(j) = abs( a_j - b_j)/2   
   > \endverbatim   
   >   
   > \param[out] WERR   
   > \verbatim   
   >          WERR is DOUBLE PRECISION array, dimension (N)   
   >          The error bound on the corresponding eigenvalue approximation   
   >          in W.   
   > \endverbatim   
   >   
   > \param[out] WL   
   > \verbatim   
   >          WL is DOUBLE PRECISION   
   > \endverbatim   
   >   
   > \param[out] WU   
   > \verbatim   
   >          WU is DOUBLE PRECISION   
   >          The interval (WL, WU] contains all the wanted eigenvalues.   
   >          If RANGE='V', then WL=VL and WU=VU.   
   >          If RANGE='A', then WL and WU are the global Gerschgorin bounds   
   >                        on the spectrum.   
   >          If RANGE='I', then WL and WU are computed by DLAEBZ from the   
   >                        index range specified.   
   > \endverbatim   
   >   
   > \param[out] IBLOCK   
   > \verbatim   
   >          IBLOCK is INTEGER array, dimension (N)   
   >          At each row/column j where E(j) is zero or small, the   
   >          matrix T is considered to split into a block diagonal   
   >          matrix.  On exit, if INFO = 0, IBLOCK(i) specifies to which   
   >          block (from 1 to the number of blocks) the eigenvalue W(i)   
   >          belongs.  (DLARRD may use the remaining N-M elements as   
   >          workspace.)   
   > \endverbatim   
   >   
   > \param[out] INDEXW   
   > \verbatim   
   >          INDEXW is INTEGER array, dimension (N)   
   >          The indices of the eigenvalues within each block (submatrix);   
   >          for example, INDEXW(i)= j and IBLOCK(i)=k imply that the   
   >          i-th eigenvalue W(i) is the j-th eigenvalue in block k.   
   > \endverbatim   
   >   
   > \param[out] WORK   
   > \verbatim   
   >          WORK is DOUBLE PRECISION array, dimension (4*N)   
   > \endverbatim   
   >   
   > \param[out] IWORK   
   > \verbatim   
   >          IWORK is INTEGER array, dimension (3*N)   
   > \endverbatim   
   >   
   > \param[out] INFO   
   > \verbatim   
   >          INFO is INTEGER   
   >          = 0:  successful exit   
   >          < 0:  if INFO = -i, the i-th argument had an illegal value   
   >          > 0:  some or all of the eigenvalues failed to converge or   
   >                were not computed:   
   >                =1 or 3: Bisection failed to converge for some   
   >                        eigenvalues; these eigenvalues are flagged by a   
   >                        negative block number.  The effect is that the   
   >                        eigenvalues may not be as accurate as the   
   >                        absolute and relative tolerances.  This is   
   >                        generally caused by unexpectedly inaccurate   
   >                        arithmetic.   
   >                =2 or 3: RANGE='I' only: Not all of the eigenvalues   
   >                        IL:IU were found.   
   >                        Effect: M < IU+1-IL   
   >                        Cause:  non-monotonic arithmetic, causing the   
   >                                Sturm sequence to be non-monotonic.   
   >                        Cure:   recalculate, using RANGE='A', and pick   
   >                                out eigenvalues IL:IU.  In some cases,   
   >                                increasing the PARAMETER "FUDGE" may   
   >                                make things work.   
   >                = 4:    RANGE='I', and the Gershgorin interval   
   >                        initially used was too small.  No eigenvalues   
   >                        were computed.   
   >                        Probable cause: your machine has sloppy   
   >                                        floating-point arithmetic.   
   >                        Cure: Increase the PARAMETER "FUDGE",   
   >                              recompile, and try again.   
   > \endverbatim   

   > \par Internal Parameters:   
    =========================   
   >   
   > \verbatim   
   >  FUDGE   DOUBLE PRECISION, default = 2   
   >          A "fudge factor" to widen the Gershgorin intervals.  Ideally,   
   >          a value of 1 should work, but on machines with sloppy   
   >          arithmetic, this needs to be larger.  The default for   
   >          publicly released versions should be large enough to handle   
   >          the worst machine around.  Note that this has no effect   
   >          on accuracy of the solution.   
   > \endverbatim   
   >   
   > \par Contributors:   
    ==================   
   >   
   >     W. Kahan, University of California, Berkeley, USA \n   
   >     Beresford Parlett, University of California, Berkeley, USA \n   
   >     Jim Demmel, University of California, Berkeley, USA \n   
   >     Inderjit Dhillon, University of Texas, Austin, USA \n   
   >     Osni Marques, LBNL/NERSC, USA \n   
   >     Christof Voemel, University of California, Berkeley, USA \n   

    Authors:   
    ========   

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

   > \date September 2012   

   > \ingroup auxOTHERauxiliary   

    =====================================================================   
   Subroutine */ int igraphdlarrd_(char *range, char *order, integer *n, doublereal 
	*vl, doublereal *vu, integer *il, integer *iu, doublereal *gers, 
	doublereal *reltol, doublereal *d__, doublereal *e, doublereal *e2, 
	doublereal *pivmin, integer *nsplit, integer *isplit, integer *m, 
	doublereal *w, doublereal *werr, doublereal *wl, doublereal *wu, 
	integer *iblock, integer *indexw, doublereal *work, integer *iwork, 
	integer *info)
{
    /* System generated locals */
    integer i__1, i__2, i__3;
    doublereal d__1, d__2;

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

    /* Local variables */
    integer i__, j, ib, ie, je, nb;
    doublereal gl;
    integer im, in;
    doublereal gu;
    integer iw, jee;
    doublereal eps;
    integer nwl;
    doublereal wlu, wul;
    integer nwu;
    doublereal tmp1, tmp2;
    integer iend, jblk, ioff, iout, itmp1, itmp2, jdisc;
    extern logical igraphlsame_(char *, char *);
    integer iinfo;
    doublereal atoli;
    integer iwoff, itmax;
    doublereal wkill, rtoli, uflow, tnorm;
    extern doublereal igraphdlamch_(char *);
    integer ibegin;
    extern /* Subroutine */ int igraphdlaebz_(integer *, integer *, integer *, 
	    integer *, integer *, integer *, doublereal *, doublereal *, 
	    doublereal *, doublereal *, doublereal *, doublereal *, integer *,
	     doublereal *, doublereal *, integer *, integer *, doublereal *, 
	    integer *, integer *);
    integer irange, idiscl, idumma[1];
    extern integer igraphilaenv_(integer *, char *, char *, integer *, integer *, 
	    integer *, integer *, ftnlen, ftnlen);
    integer idiscu;
    logical ncnvrg, toofew;


/*  -- LAPACK auxiliary 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   


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


       Parameter adjustments */
    --iwork;
    --work;
    --indexw;
    --iblock;
    --werr;
    --w;
    --isplit;
    --e2;
    --e;
    --d__;
    --gers;

    /* Function Body */
    *info = 0;

/*     Decode RANGE */

    if (igraphlsame_(range, "A")) {
	irange = 1;
    } else if (igraphlsame_(range, "V")) {
	irange = 2;
    } else if (igraphlsame_(range, "I")) {
	irange = 3;
    } else {
	irange = 0;
    }

/*     Check for Errors */

    if (irange <= 0) {
	*info = -1;
    } else if (! (igraphlsame_(order, "B") || igraphlsame_(order, 
	    "E"))) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (irange == 2) {
	if (*vl >= *vu) {
	    *info = -5;
	}
    } else if (irange == 3 && (*il < 1 || *il > max(1,*n))) {
	*info = -6;
    } else if (irange == 3 && (*iu < min(*n,*il) || *iu > *n)) {
	*info = -7;
    }

    if (*info != 0) {
	return 0;
    }
/*     Initialize error flags */
    *info = 0;
    ncnvrg = FALSE_;
    toofew = FALSE_;
/*     Quick return if possible */
    *m = 0;
    if (*n == 0) {
	return 0;
    }
/*     Simplification: */
    if (irange == 3 && *il == 1 && *iu == *n) {
	irange = 1;
    }
/*     Get machine constants */
    eps = igraphdlamch_("P");
    uflow = igraphdlamch_("U");
/*     Special Case when N=1   
       Treat case of 1x1 matrix for quick return */
    if (*n == 1) {
	if (irange == 1 || irange == 2 && d__[1] > *vl && d__[1] <= *vu || 
		irange == 3 && *il == 1 && *iu == 1) {
	    *m = 1;
	    w[1] = d__[1];
/*           The computation error of the eigenvalue is zero */
	    werr[1] = 0.;
	    iblock[1] = 1;
	    indexw[1] = 1;
	}
	return 0;
    }
/*     NB is the minimum vector length for vector bisection, or 0   
       if only scalar is to be done. */
    nb = igraphilaenv_(&c__1, "DSTEBZ", " ", n, &c_n1, &c_n1, &c_n1, (ftnlen)6, (
	    ftnlen)1);
    if (nb <= 1) {
	nb = 0;
    }
/*     Find global spectral radius */
    gl = d__[1];
    gu = d__[1];
    i__1 = *n;
    for (i__ = 1; i__ <= i__1; ++i__) {
/* Computing MIN */
	d__1 = gl, d__2 = gers[(i__ << 1) - 1];
	gl = min(d__1,d__2);
/* Computing MAX */
	d__1 = gu, d__2 = gers[i__ * 2];
	gu = max(d__1,d__2);
/* L5: */
    }
/*     Compute global Gerschgorin bounds and spectral diameter   
   Computing MAX */
    d__1 = abs(gl), d__2 = abs(gu);
    tnorm = max(d__1,d__2);
    gl = gl - tnorm * 2. * eps * *n - *pivmin * 4.;
    gu = gu + tnorm * 2. * eps * *n + *pivmin * 4.;
/*     [JAN/28/2009] remove the line below since SPDIAM variable not use   
       SPDIAM = GU - GL   
       Input arguments for DLAEBZ:   
       The relative tolerance.  An interval (a,b] lies within   
       "relative tolerance" if  b-a < RELTOL*max(|a|,|b|), */
    rtoli = *reltol;
/*     Set the absolute tolerance for interval convergence to zero to force   
       interval convergence based on relative size of the interval.   
       This is dangerous because intervals might not converge when RELTOL is   
       small. But at least a very small number should be selected so that for   
       strongly graded matrices, the code can get relatively accurate   
       eigenvalues. */
    atoli = uflow * 4. + *pivmin * 4.;
    if (irange == 3) {
/*        RANGE='I': Compute an interval containing eigenvalues   
          IL through IU. The initial interval [GL,GU] from the global   
          Gerschgorin bounds GL and GU is refined by DLAEBZ. */
	itmax = (integer) ((log(tnorm + *pivmin) - log(*pivmin)) / log(2.)) + 
		2;
	work[*n + 1] = gl;
	work[*n + 2] = gl;
	work[*n + 3] = gu;
	work[*n + 4] = gu;
	work[*n + 5] = gl;
	work[*n + 6] = gu;
	iwork[1] = -1;
	iwork[2] = -1;
	iwork[3] = *n + 1;
	iwork[4] = *n + 1;
	iwork[5] = *il - 1;
	iwork[6] = *iu;

	igraphdlaebz_(&c__3, &itmax, n, &c__2, &c__2, &nb, &atoli, &rtoli, pivmin, &
		d__[1], &e[1], &e2[1], &iwork[5], &work[*n + 1], &work[*n + 5]
		, &iout, &iwork[1], &w[1], &iblock[1], &iinfo);
	if (iinfo != 0) {
	    *info = iinfo;
	    return 0;
	}
/*        On exit, output intervals may not be ordered by ascending negcount */
	if (iwork[6] == *iu) {
	    *wl = work[*n + 1];
	    wlu = work[*n + 3];
	    nwl = iwork[1];
	    *wu = work[*n + 4];
	    wul = work[*n + 2];
	    nwu = iwork[4];
	} else {
	    *wl = work[*n + 2];
	    wlu = work[*n + 4];
	    nwl = iwork[2];
	    *wu = work[*n + 3];
	    wul = work[*n + 1];
	    nwu = iwork[3];
	}
/*        On exit, the interval [WL, WLU] contains a value with negcount NWL,   
          and [WUL, WU] contains a value with negcount NWU. */
	if (nwl < 0 || nwl >= *n || nwu < 1 || nwu > *n) {
	    *info = 4;
	    return 0;
	}
    } else if (irange == 2) {
	*wl = *vl;
	*wu = *vu;
    } else if (irange == 1) {
	*wl = gl;
	*wu = gu;
    }
/*     Find Eigenvalues -- Loop Over blocks and recompute NWL and NWU.   
       NWL accumulates the number of eigenvalues .le. WL,   
       NWU accumulates the number of eigenvalues .le. WU */
    *m = 0;
    iend = 0;
    *info = 0;
    nwl = 0;
    nwu = 0;

    i__1 = *nsplit;
    for (jblk = 1; jblk <= i__1; ++jblk) {
	ioff = iend;
	ibegin = ioff + 1;
	iend = isplit[jblk];
	in = iend - ioff;

	if (in == 1) {
/*           1x1 block */
	    if (*wl >= d__[ibegin] - *pivmin) {
		++nwl;
	    }
	    if (*wu >= d__[ibegin] - *pivmin) {
		++nwu;
	    }
	    if (irange == 1 || *wl < d__[ibegin] - *pivmin && *wu >= d__[
		    ibegin] - *pivmin) {
		++(*m);
		w[*m] = d__[ibegin];
		werr[*m] = 0.;
/*              The gap for a single block doesn't matter for the later   
                algorithm and is assigned an arbitrary large value */
		iblock[*m] = jblk;
		indexw[*m] = 1;
	    }
/*        Disabled 2x2 case because of a failure on the following matrix   
          RANGE = 'I', IL = IU = 4   
            Original Tridiagonal, d = [   
             -0.150102010615740E+00   
             -0.849897989384260E+00   
             -0.128208148052635E-15   
              0.128257718286320E-15   
            ];   
            e = [   
             -0.357171383266986E+00   
             -0.180411241501588E-15   
             -0.175152352710251E-15   
            ];   

           ELSE IF( IN.EQ.2 ) THEN   
   *           2x2 block   
              DISC = SQRT( (HALF*(D(IBEGIN)-D(IEND)))**2 + E(IBEGIN)**2 )   
              TMP1 = HALF*(D(IBEGIN)+D(IEND))   
              L1 = TMP1 - DISC   
              IF( WL.GE. L1-PIVMIN )   
       $         NWL = NWL + 1   
              IF( WU.GE. L1-PIVMIN )   
       $         NWU = NWU + 1   
              IF( IRANGE.EQ.ALLRNG .OR. ( WL.LT.L1-PIVMIN .AND. WU.GE.   
       $          L1-PIVMIN ) ) THEN   
                 M = M + 1   
                 W( M ) = L1   
   *              The uncertainty of eigenvalues of a 2x2 matrix is very small   
                 WERR( M ) = EPS * ABS( W( M ) ) * TWO   
                 IBLOCK( M ) = JBLK   
                 INDEXW( M ) = 1   
              ENDIF   
              L2 = TMP1 + DISC   
              IF( WL.GE. L2-PIVMIN )   
       $         NWL = NWL + 1   
              IF( WU.GE. L2-PIVMIN )   
       $         NWU = NWU + 1   
              IF( IRANGE.EQ.ALLRNG .OR. ( WL.LT.L2-PIVMIN .AND. WU.GE.   
       $          L2-PIVMIN ) ) THEN   
                 M = M + 1   
                 W( M ) = L2   
   *              The uncertainty of eigenvalues of a 2x2 matrix is very small   
                 WERR( M ) = EPS * ABS( W( M ) ) * TWO   
                 IBLOCK( M ) = JBLK   
                 INDEXW( M ) = 2   
              ENDIF */
	} else {
/*           General Case - block of size IN >= 2   
             Compute local Gerschgorin interval and use it as the initial   
             interval for DLAEBZ */
	    gu = d__[ibegin];
	    gl = d__[ibegin];
	    tmp1 = 0.;
	    i__2 = iend;
	    for (j = ibegin; j <= i__2; ++j) {
/* Computing MIN */
		d__1 = gl, d__2 = gers[(j << 1) - 1];
		gl = min(d__1,d__2);
/* Computing MAX */
		d__1 = gu, d__2 = gers[j * 2];
		gu = max(d__1,d__2);
/* L40: */
	    }
/*           [JAN/28/2009]   
             change SPDIAM by TNORM in lines 2 and 3 thereafter   
             line 1: remove computation of SPDIAM (not useful anymore)   
             SPDIAM = GU - GL   
             GL = GL - FUDGE*SPDIAM*EPS*IN - FUDGE*PIVMIN   
             GU = GU + FUDGE*SPDIAM*EPS*IN + FUDGE*PIVMIN */
	    gl = gl - tnorm * 2. * eps * in - *pivmin * 2.;
	    gu = gu + tnorm * 2. * eps * in + *pivmin * 2.;

	    if (irange > 1) {
		if (gu < *wl) {
/*                 the local block contains none of the wanted eigenvalues */
		    nwl += in;
		    nwu += in;
		    goto L70;
		}
/*              refine search interval if possible, only range (WL,WU] matters */
		gl = max(gl,*wl);
		gu = min(gu,*wu);
		if (gl >= gu) {
		    goto L70;
		}
	    }
/*           Find negcount of initial interval boundaries GL and GU */
	    work[*n + 1] = gl;
	    work[*n + in + 1] = gu;
	    igraphdlaebz_(&c__1, &c__0, &in, &in, &c__1, &nb, &atoli, &rtoli, 
		    pivmin, &d__[ibegin], &e[ibegin], &e2[ibegin], idumma, &
		    work[*n + 1], &work[*n + (in << 1) + 1], &im, &iwork[1], &
		    w[*m + 1], &iblock[*m + 1], &iinfo);
	    if (iinfo != 0) {
		*info = iinfo;
		return 0;
	    }

	    nwl += iwork[1];
	    nwu += iwork[in + 1];
	    iwoff = *m - iwork[1];
/*           Compute Eigenvalues */
	    itmax = (integer) ((log(gu - gl + *pivmin) - log(*pivmin)) / log(
		    2.)) + 2;
	    igraphdlaebz_(&c__2, &itmax, &in, &in, &c__1, &nb, &atoli, &rtoli, 
		    pivmin, &d__[ibegin], &e[ibegin], &e2[ibegin], idumma, &
		    work[*n + 1], &work[*n + (in << 1) + 1], &iout, &iwork[1],
		     &w[*m + 1], &iblock[*m + 1], &iinfo);
	    if (iinfo != 0) {
		*info = iinfo;
		return 0;
	    }

/*           Copy eigenvalues into W and IBLOCK   
             Use -JBLK for block number for unconverged eigenvalues.   
             Loop over the number of output intervals from DLAEBZ */
	    i__2 = iout;
	    for (j = 1; j <= i__2; ++j) {
/*              eigenvalue approximation is middle point of interval */
		tmp1 = (work[j + *n] + work[j + in + *n]) * .5;
/*              semi length of error interval */
		tmp2 = (d__1 = work[j + *n] - work[j + in + *n], abs(d__1)) * 
			.5;
		if (j > iout - iinfo) {
/*                 Flag non-convergence. */
		    ncnvrg = TRUE_;
		    ib = -jblk;
		} else {
		    ib = jblk;
		}
		i__3 = iwork[j + in] + iwoff;
		for (je = iwork[j] + 1 + iwoff; je <= i__3; ++je) {
		    w[je] = tmp1;
		    werr[je] = tmp2;
		    indexw[je] = je - iwoff;
		    iblock[je] = ib;
/* L50: */
		}
/* L60: */
	    }

	    *m += im;
	}
L70:
	;
    }
/*     If RANGE='I', then (WL,WU) contains eigenvalues NWL+1,...,NWU   
       If NWL+1 < IL or NWU > IU, discard extra eigenvalues. */
    if (irange == 3) {
	idiscl = *il - 1 - nwl;
	idiscu = nwu - *iu;

	if (idiscl > 0) {
	    im = 0;
	    i__1 = *m;
	    for (je = 1; je <= i__1; ++je) {
/*              Remove some of the smallest eigenvalues from the left so that   
                at the end IDISCL =0. Move all eigenvalues up to the left. */
		if (w[je] <= wlu && idiscl > 0) {
		    --idiscl;
		} else {
		    ++im;
		    w[im] = w[je];
		    werr[im] = werr[je];
		    indexw[im] = indexw[je];
		    iblock[im] = iblock[je];
		}
/* L80: */
	    }
	    *m = im;
	}
	if (idiscu > 0) {
/*           Remove some of the largest eigenvalues from the right so that   
             at the end IDISCU =0. Move all eigenvalues up to the left. */
	    im = *m + 1;
	    for (je = *m; je >= 1; --je) {
		if (w[je] >= wul && idiscu > 0) {
		    --idiscu;
		} else {
		    --im;
		    w[im] = w[je];
		    werr[im] = werr[je];
		    indexw[im] = indexw[je];
		    iblock[im] = iblock[je];
		}
/* L81: */
	    }
	    jee = 0;
	    i__1 = *m;
	    for (je = im; je <= i__1; ++je) {
		++jee;
		w[jee] = w[je];
		werr[jee] = werr[je];
		indexw[jee] = indexw[je];
		iblock[jee] = iblock[je];
/* L82: */
	    }
	    *m = *m - im + 1;
	}
	if (idiscl > 0 || idiscu > 0) {
/*           Code to deal with effects of bad arithmetic. (If N(w) is   
             monotone non-decreasing, this should never happen.)   
             Some low eigenvalues to be discarded are not in (WL,WLU],   
             or high eigenvalues to be discarded are not in (WUL,WU]   
             so just kill off the smallest IDISCL/largest IDISCU   
             eigenvalues, by marking the corresponding IBLOCK = 0 */
	    if (idiscl > 0) {
		wkill = *wu;
		i__1 = idiscl;
		for (jdisc = 1; jdisc <= i__1; ++jdisc) {
		    iw = 0;
		    i__2 = *m;
		    for (je = 1; je <= i__2; ++je) {
			if (iblock[je] != 0 && (w[je] < wkill || iw == 0)) {
			    iw = je;
			    wkill = w[je];
			}
/* L90: */
		    }
		    iblock[iw] = 0;
/* L100: */
		}
	    }
	    if (idiscu > 0) {
		wkill = *wl;
		i__1 = idiscu;
		for (jdisc = 1; jdisc <= i__1; ++jdisc) {
		    iw = 0;
		    i__2 = *m;
		    for (je = 1; je <= i__2; ++je) {
			if (iblock[je] != 0 && (w[je] >= wkill || iw == 0)) {
			    iw = je;
			    wkill = w[je];
			}
/* L110: */
		    }
		    iblock[iw] = 0;
/* L120: */
		}
	    }
/*           Now erase all eigenvalues with IBLOCK set to zero */
	    im = 0;
	    i__1 = *m;
	    for (je = 1; je <= i__1; ++je) {
		if (iblock[je] != 0) {
		    ++im;
		    w[im] = w[je];
		    werr[im] = werr[je];
		    indexw[im] = indexw[je];
		    iblock[im] = iblock[je];
		}
/* L130: */
	    }
	    *m = im;
	}
	if (idiscl < 0 || idiscu < 0) {
	    toofew = TRUE_;
	}
    }

    if (irange == 1 && *m != *n || irange == 3 && *m != *iu - *il + 1) {
	toofew = TRUE_;
    }
/*     If ORDER='B', do nothing the eigenvalues are already sorted by   
          block.   
       If ORDER='E', sort the eigenvalues from smallest to largest */
    if (igraphlsame_(order, "E") && *nsplit > 1) {
	i__1 = *m - 1;
	for (je = 1; je <= i__1; ++je) {
	    ie = 0;
	    tmp1 = w[je];
	    i__2 = *m;
	    for (j = je + 1; j <= i__2; ++j) {
		if (w[j] < tmp1) {
		    ie = j;
		    tmp1 = w[j];
		}
/* L140: */
	    }
	    if (ie != 0) {
		tmp2 = werr[ie];
		itmp1 = iblock[ie];
		itmp2 = indexw[ie];
		w[ie] = w[je];
		werr[ie] = werr[je];
		iblock[ie] = iblock[je];
		indexw[ie] = indexw[je];
		w[je] = tmp1;
		werr[je] = tmp2;
		iblock[je] = itmp1;
		indexw[je] = itmp2;
	    }
/* L150: */
	}
    }

    *info = 0;
    if (ncnvrg) {
	++(*info);
    }
    if (toofew) {
	*info += 2;
    }
    return 0;

/*     End of DLARRD */

} /* igraphdlarrd_ */