OpenBLAS/lapack-netlib/SRC/dlarrb.c

/* f2c.h  --  Standard Fortran to C header file */

/**  barf  [ba:rf]  2.  "He suggested using FORTRAN, and everybody barfed."

	- From The Shogakukan DICTIONARY OF NEW ENGLISH (Second edition) */

#ifndef F2C_INCLUDE
#define F2C_INCLUDE

#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <complex.h>
#ifdef complex
#undef complex
#endif
#ifdef I
#undef I
#endif

#if defined(_WIN64)
typedef long long BLASLONG;
typedef unsigned long long BLASULONG;
#else
typedef long BLASLONG;
typedef unsigned long BLASULONG;
#endif

#ifdef LAPACK_ILP64
typedef BLASLONG blasint;
#if defined(_WIN64)
#define blasabs(x) llabs(x)
#else
#define blasabs(x) labs(x)
#endif
#else
typedef int blasint;
#define blasabs(x) abs(x)
#endif

typedef blasint integer;

typedef unsigned int uinteger;
typedef char *address;
typedef short int shortint;
typedef float real;
typedef double doublereal;
typedef struct { real r, i; } complex;
typedef struct { doublereal r, i; } doublecomplex;
static inline _Complex float Cf(complex *z) {return z->r + z->i*_Complex_I;}
static inline _Complex double Cd(doublecomplex *z) {return z->r + z->i*_Complex_I;}
static inline _Complex float * _pCf(complex *z) {return (_Complex float*)z;}
static inline _Complex double * _pCd(doublecomplex *z) {return (_Complex double*)z;}
#define pCf(z) (*_pCf(z))
#define pCd(z) (*_pCd(z))
typedef int logical;
typedef short int shortlogical;
typedef char logical1;
typedef char integer1;

#define TRUE_ (1)
#define FALSE_ (0)

/* Extern is for use with -E */
#ifndef Extern
#define Extern extern
#endif

/* I/O stuff */

typedef int flag;
typedef int ftnlen;
typedef int ftnint;

/*external read, write*/
typedef struct
{	flag cierr;
	ftnint ciunit;
	flag ciend;
	char *cifmt;
	ftnint cirec;
} cilist;

/*internal read, write*/
typedef struct
{	flag icierr;
	char *iciunit;
	flag iciend;
	char *icifmt;
	ftnint icirlen;
	ftnint icirnum;
} icilist;

/*open*/
typedef struct
{	flag oerr;
	ftnint ounit;
	char *ofnm;
	ftnlen ofnmlen;
	char *osta;
	char *oacc;
	char *ofm;
	ftnint orl;
	char *oblnk;
} olist;

/*close*/
typedef struct
{	flag cerr;
	ftnint cunit;
	char *csta;
} cllist;

/*rewind, backspace, endfile*/
typedef struct
{	flag aerr;
	ftnint aunit;
} alist;

/* inquire */
typedef struct
{	flag inerr;
	ftnint inunit;
	char *infile;
	ftnlen infilen;
	ftnint	*inex;	/*parameters in standard's order*/
	ftnint	*inopen;
	ftnint	*innum;
	ftnint	*innamed;
	char	*inname;
	ftnlen	innamlen;
	char	*inacc;
	ftnlen	inacclen;
	char	*inseq;
	ftnlen	inseqlen;
	char 	*indir;
	ftnlen	indirlen;
	char	*infmt;
	ftnlen	infmtlen;
	char	*inform;
	ftnint	informlen;
	char	*inunf;
	ftnlen	inunflen;
	ftnint	*inrecl;
	ftnint	*innrec;
	char	*inblank;
	ftnlen	inblanklen;
} inlist;

#define VOID void

union Multitype {	/* for multiple entry points */
	integer1 g;
	shortint h;
	integer i;
	/* longint j; */
	real r;
	doublereal d;
	complex c;
	doublecomplex z;
	};

typedef union Multitype Multitype;

struct Vardesc {	/* for Namelist */
	char *name;
	char *addr;
	ftnlen *dims;
	int  type;
	};
typedef struct Vardesc Vardesc;

struct Namelist {
	char *name;
	Vardesc **vars;
	int nvars;
	};
typedef struct Namelist Namelist;

#define abs(x) ((x) >= 0 ? (x) : -(x))
#define dabs(x) (fabs(x))
#define f2cmin(a,b) ((a) <= (b) ? (a) : (b))
#define f2cmax(a,b) ((a) >= (b) ? (a) : (b))
#define dmin(a,b) (f2cmin(a,b))
#define dmax(a,b) (f2cmax(a,b))
#define bit_test(a,b)	((a) >> (b) & 1)
#define bit_clear(a,b)	((a) & ~((uinteger)1 << (b)))
#define bit_set(a,b)	((a) |  ((uinteger)1 << (b)))

#define abort_() { sig_die("Fortran abort routine called", 1); }
#define c_abs(z) (cabsf(Cf(z)))
#define c_cos(R,Z) { pCf(R)=ccos(Cf(Z)); }
#define c_div(c, a, b) {pCf(c) = Cf(a)/Cf(b);}
#define z_div(c, a, b) {pCd(c) = Cd(a)/Cd(b);}
#define c_exp(R, Z) {pCf(R) = cexpf(Cf(Z));}
#define c_log(R, Z) {pCf(R) = clogf(Cf(Z));}
#define c_sin(R, Z) {pCf(R) = csinf(Cf(Z));}
//#define c_sqrt(R, Z) {*(R) = csqrtf(Cf(Z));}
#define c_sqrt(R, Z) {pCf(R) = csqrtf(Cf(Z));}
#define d_abs(x) (fabs(*(x)))
#define d_acos(x) (acos(*(x)))
#define d_asin(x) (asin(*(x)))
#define d_atan(x) (atan(*(x)))
#define d_atn2(x, y) (atan2(*(x),*(y)))
#define d_cnjg(R, Z) { pCd(R) = conj(Cd(Z)); }
#define r_cnjg(R, Z) { pCf(R) = conj(Cf(Z)); }
#define d_cos(x) (cos(*(x)))
#define d_cosh(x) (cosh(*(x)))
#define d_dim(__a, __b) ( *(__a) > *(__b) ? *(__a) - *(__b) : 0.0 )
#define d_exp(x) (exp(*(x)))
#define d_imag(z) (cimag(Cd(z)))
#define r_imag(z) (cimag(Cf(z)))
#define d_int(__x) (*(__x)>0 ? floor(*(__x)) : -floor(- *(__x)))
#define r_int(__x) (*(__x)>0 ? floor(*(__x)) : -floor(- *(__x)))
#define d_lg10(x) ( 0.43429448190325182765 * log(*(x)) )
#define r_lg10(x) ( 0.43429448190325182765 * log(*(x)) )
#define d_log(x) (log(*(x)))
#define d_mod(x, y) (fmod(*(x), *(y)))
#define u_nint(__x) ((__x)>=0 ? floor((__x) + .5) : -floor(.5 - (__x)))
#define d_nint(x) u_nint(*(x))
#define u_sign(__a,__b) ((__b) >= 0 ? ((__a) >= 0 ? (__a) : -(__a)) : -((__a) >= 0 ? (__a) : -(__a)))
#define d_sign(a,b) u_sign(*(a),*(b))
#define r_sign(a,b) u_sign(*(a),*(b))
#define d_sin(x) (sin(*(x)))
#define d_sinh(x) (sinh(*(x)))
#define d_sqrt(x) (sqrt(*(x)))
#define d_tan(x) (tan(*(x)))
#define d_tanh(x) (tanh(*(x)))
#define i_abs(x) abs(*(x))
#define i_dnnt(x) ((integer)u_nint(*(x)))
#define i_len(s, n) (n)
#define i_nint(x) ((integer)u_nint(*(x)))
#define i_sign(a,b) ((integer)u_sign((integer)*(a),(integer)*(b)))
#define pow_dd(ap, bp) ( pow(*(ap), *(bp)))
#define pow_si(B,E) spow_ui(*(B),*(E))
#define pow_ri(B,E) spow_ui(*(B),*(E))
#define pow_di(B,E) dpow_ui(*(B),*(E))
#define pow_zi(p, a, b) {pCd(p) = zpow_ui(Cd(a), *(b));}
#define pow_ci(p, a, b) {pCf(p) = cpow_ui(Cf(a), *(b));}
#define pow_zz(R,A,B) {pCd(R) = cpow(Cd(A),*(B));}
#define s_cat(lpp, rpp, rnp, np, llp) { 	ftnlen i, nc, ll; char *f__rp, *lp; 	ll = (llp); lp = (lpp); 	for(i=0; i < (int)*(np); ++i) {         	nc = ll; 	        if((rnp)[i] < nc) nc = (rnp)[i]; 	        ll -= nc;         	f__rp = (rpp)[i]; 	        while(--nc >= 0) *lp++ = *(f__rp)++;         } 	while(--ll >= 0) *lp++ = ' '; }
#define s_cmp(a,b,c,d) ((integer)strncmp((a),(b),f2cmin((c),(d))))
#define s_copy(A,B,C,D) { int __i,__m; for (__i=0, __m=f2cmin((C),(D)); __i<__m && (B)[__i] != 0; ++__i) (A)[__i] = (B)[__i]; }
#define sig_die(s, kill) { exit(1); }
#define s_stop(s, n) {exit(0);}
static char junk[] = "\n@(#)LIBF77 VERSION 19990503\n";
#define z_abs(z) (cabs(Cd(z)))
#define z_exp(R, Z) {pCd(R) = cexp(Cd(Z));}
#define z_sqrt(R, Z) {pCd(R) = csqrt(Cd(Z));}
#define myexit_() break;
#define mycycle() continue;
#define myceiling(w) {ceil(w)}
#define myhuge(w) {HUGE_VAL}
//#define mymaxloc_(w,s,e,n) {if (sizeof(*(w)) == sizeof(double)) dmaxloc_((w),*(s),*(e),n); else dmaxloc_((w),*(s),*(e),n);}
#define mymaxloc(w,s,e,n) {dmaxloc_(w,*(s),*(e),n)}

/* procedure parameter types for -A and -C++ */

#define F2C_proc_par_types 1
#ifdef __cplusplus
typedef logical (*L_fp)(...);
#else
typedef logical (*L_fp)();
#endif

static float spow_ui(float x, integer n) {
	float pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static double dpow_ui(double x, integer n) {
	double pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static _Complex float cpow_ui(_Complex float x, integer n) {
	_Complex float pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static _Complex double zpow_ui(_Complex double x, integer n) {
	_Complex double pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static integer pow_ii(integer x, integer n) {
	integer pow; unsigned long int u;
	if (n <= 0) {
		if (n == 0 || x == 1) pow = 1;
		else if (x != -1) pow = x == 0 ? 1/x : 0;
		else n = -n;
	}
	if ((n > 0) || !(n == 0 || x == 1 || x != -1)) {
		u = n;
		for(pow = 1; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static integer dmaxloc_(double *w, integer s, integer e, integer *n)
{
	double m; integer i, mi;
	for(m=w[s-1], mi=s, i=s+1; i<=e; i++)
		if (w[i-1]>m) mi=i ,m=w[i-1];
	return mi-s+1;
}
static integer smaxloc_(float *w, integer s, integer e, integer *n)
{
	float m; integer i, mi;
	for(m=w[s-1], mi=s, i=s+1; i<=e; i++)
		if (w[i-1]>m) mi=i ,m=w[i-1];
	return mi-s+1;
}
static inline void cdotc_(complex *z, integer *n_, complex *x, integer *incx_, complex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex float zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conjf(Cf(&x[i])) * Cf(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conjf(Cf(&x[i*incx])) * Cf(&y[i*incy]);
		}
	}
	pCf(z) = zdotc;
}
static inline void zdotc_(doublecomplex *z, integer *n_, doublecomplex *x, integer *incx_, doublecomplex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex double zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conj(Cd(&x[i])) * Cd(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conj(Cd(&x[i*incx])) * Cd(&y[i*incy]);
		}
	}
	pCd(z) = zdotc;
}	
static inline void cdotu_(complex *z, integer *n_, complex *x, integer *incx_, complex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex float zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cf(&x[i]) * Cf(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cf(&x[i*incx]) * Cf(&y[i*incy]);
		}
	}
	pCf(z) = zdotc;
}
static inline void zdotu_(doublecomplex *z, integer *n_, doublecomplex *x, integer *incx_, doublecomplex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex double zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cd(&x[i]) * Cd(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cd(&x[i*incx]) * Cd(&y[i*incy]);
		}
	}
	pCd(z) = zdotc;
}
#endif
/*  -- translated by f2c (version 20000121).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/



/* > \brief \b DLARRB provides limited bisection to locate eigenvalues for more accuracy. */

/*  =========== DOCUMENTATION =========== */

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

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

/*  Definition: */
/*  =========== */

/*       SUBROUTINE DLARRB( N, D, LLD, IFIRST, ILAST, RTOL1, */
/*                          RTOL2, OFFSET, W, WGAP, WERR, WORK, IWORK, */
/*                          PIVMIN, SPDIAM, TWIST, INFO ) */

/*       INTEGER            IFIRST, ILAST, INFO, N, OFFSET, TWIST */
/*       DOUBLE PRECISION   PIVMIN, RTOL1, RTOL2, SPDIAM */
/*       INTEGER            IWORK( * ) */
/*       DOUBLE PRECISION   D( * ), LLD( * ), W( * ), */
/*      $                   WERR( * ), WGAP( * ), WORK( * ) */


/* > \par Purpose: */
/*  ============= */
/* > */
/* > \verbatim */
/* > */
/* > Given the relatively robust representation(RRR) L D L^T, DLARRB */
/* > does "limited" bisection to refine the eigenvalues of L D L^T, */
/* > W( IFIRST-OFFSET ) through W( ILAST-OFFSET ), to more accuracy. Initial */
/* > guesses for these eigenvalues are input in W, the corresponding estimate */
/* > of the error in these guesses and their gaps are input in WERR */
/* > and WGAP, respectively. During bisection, intervals */
/* > [left, right] are maintained by storing their mid-points and */
/* > semi-widths in the arrays W and WERR respectively. */
/* > \endverbatim */

/*  Arguments: */
/*  ========== */

/* > \param[in] N */
/* > \verbatim */
/* >          N is INTEGER */
/* >          The order of the matrix. */
/* > \endverbatim */
/* > */
/* > \param[in] D */
/* > \verbatim */
/* >          D is DOUBLE PRECISION array, dimension (N) */
/* >          The N diagonal elements of the diagonal matrix D. */
/* > \endverbatim */
/* > */
/* > \param[in] LLD */
/* > \verbatim */
/* >          LLD is DOUBLE PRECISION array, dimension (N-1) */
/* >          The (N-1) elements L(i)*L(i)*D(i). */
/* > \endverbatim */
/* > */
/* > \param[in] IFIRST */
/* > \verbatim */
/* >          IFIRST is INTEGER */
/* >          The index of the first eigenvalue to be computed. */
/* > \endverbatim */
/* > */
/* > \param[in] ILAST */
/* > \verbatim */
/* >          ILAST is INTEGER */
/* >          The index of the last eigenvalue to be computed. */
/* > \endverbatim */
/* > */
/* > \param[in] RTOL1 */
/* > \verbatim */
/* >          RTOL1 is DOUBLE PRECISION */
/* > \endverbatim */
/* > */
/* > \param[in] RTOL2 */
/* > \verbatim */
/* >          RTOL2 is DOUBLE PRECISION */
/* >          Tolerance for the convergence of the bisection intervals. */
/* >          An interval [LEFT,RIGHT] has converged if */
/* >          RIGHT-LEFT < MAX( RTOL1*GAP, RTOL2*MAX(|LEFT|,|RIGHT|) ) */
/* >          where GAP is the (estimated) distance to the nearest */
/* >          eigenvalue. */
/* > \endverbatim */
/* > */
/* > \param[in] OFFSET */
/* > \verbatim */
/* >          OFFSET is INTEGER */
/* >          Offset for the arrays W, WGAP and WERR, i.e., the IFIRST-OFFSET */
/* >          through ILAST-OFFSET elements of these arrays are to be used. */
/* > \endverbatim */
/* > */
/* > \param[in,out] W */
/* > \verbatim */
/* >          W is DOUBLE PRECISION array, dimension (N) */
/* >          On input, W( IFIRST-OFFSET ) through W( ILAST-OFFSET ) are */
/* >          estimates of the eigenvalues of L D L^T indexed IFIRST through */
/* >          ILAST. */
/* >          On output, these estimates are refined. */
/* > \endverbatim */
/* > */
/* > \param[in,out] WGAP */
/* > \verbatim */
/* >          WGAP is DOUBLE PRECISION array, dimension (N-1) */
/* >          On input, the (estimated) gaps between consecutive */
/* >          eigenvalues of L D L^T, i.e., WGAP(I-OFFSET) is the gap between */
/* >          eigenvalues I and I+1. Note that if IFIRST = ILAST */
/* >          then WGAP(IFIRST-OFFSET) must be set to ZERO. */
/* >          On output, these gaps are refined. */
/* > \endverbatim */
/* > */
/* > \param[in,out] WERR */
/* > \verbatim */
/* >          WERR is DOUBLE PRECISION array, dimension (N) */
/* >          On input, WERR( IFIRST-OFFSET ) through WERR( ILAST-OFFSET ) are */
/* >          the errors in the estimates of the corresponding elements in W. */
/* >          On output, these errors are refined. */
/* > \endverbatim */
/* > */
/* > \param[out] WORK */
/* > \verbatim */
/* >          WORK is DOUBLE PRECISION array, dimension (2*N) */
/* >          Workspace. */
/* > \endverbatim */
/* > */
/* > \param[out] IWORK */
/* > \verbatim */
/* >          IWORK is INTEGER array, dimension (2*N) */
/* >          Workspace. */
/* > \endverbatim */
/* > */
/* > \param[in] PIVMIN */
/* > \verbatim */
/* >          PIVMIN is DOUBLE PRECISION */
/* >          The minimum pivot in the Sturm sequence. */
/* > \endverbatim */
/* > */
/* > \param[in] SPDIAM */
/* > \verbatim */
/* >          SPDIAM is DOUBLE PRECISION */
/* >          The spectral diameter of the matrix. */
/* > \endverbatim */
/* > */
/* > \param[in] TWIST */
/* > \verbatim */
/* >          TWIST is INTEGER */
/* >          The twist index for the twisted factorization that is used */
/* >          for the negcount. */
/* >          TWIST = N: Compute negcount from L D L^T - LAMBDA I = L+ D+ L+^T */
/* >          TWIST = 1: Compute negcount from L D L^T - LAMBDA I = U- D- U-^T */
/* >          TWIST = R: Compute negcount from L D L^T - LAMBDA I = N(r) D(r) N(r) */
/* > \endverbatim */
/* > */
/* > \param[out] INFO */
/* > \verbatim */
/* >          INFO is INTEGER */
/* >          Error flag. */
/* > \endverbatim */

/*  Authors: */
/*  ======== */

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

/* > \date June 2017 */

/* > \ingroup OTHERauxiliary */

/* > \par Contributors: */
/*  ================== */
/* > */
/* > 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 */

/*  ===================================================================== */
/* Subroutine */ int dlarrb_(integer *n, doublereal *d__, doublereal *lld, 
	integer *ifirst, integer *ilast, doublereal *rtol1, doublereal *rtol2,
	 integer *offset, doublereal *w, doublereal *wgap, doublereal *werr, 
	doublereal *work, integer *iwork, doublereal *pivmin, doublereal *
	spdiam, integer *twist, integer *info)
{
    /* System generated locals */
    integer i__1;
    doublereal d__1, d__2;

    /* Local variables */
    doublereal back, lgap, rgap, left;
    integer iter, nint, prev, next, i__, k, r__;
    doublereal cvrgd, right, width;
    integer i1, ii, ip;
    extern integer dlaneg_(integer *, doublereal *, doublereal *, doublereal *
	    , doublereal *, integer *);
    integer negcnt;
    doublereal mnwdth;
    integer olnint, maxitr;
    doublereal gap, mid, tmp;


/*  -- LAPACK auxiliary routine (version 3.7.1) -- */
/*  -- LAPACK is a software package provided by Univ. of Tennessee,    -- */
/*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
/*     June 2017 */


/*  ===================================================================== */



    /* Parameter adjustments */
    --iwork;
    --work;
    --werr;
    --wgap;
    --w;
    --lld;
    --d__;

    /* Function Body */
    *info = 0;

/*     Quick return if possible */

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

    maxitr = (integer) ((log(*spdiam + *pivmin) - log(*pivmin)) / log(2.)) + 
	    2;
    mnwdth = *pivmin * 2.;

    r__ = *twist;
    if (r__ < 1 || r__ > *n) {
	r__ = *n;
    }

/*     Initialize unconverged intervals in [ WORK(2*I-1), WORK(2*I) ]. */
/*     The Sturm Count, Count( WORK(2*I-1) ) is arranged to be I-1, while */
/*     Count( WORK(2*I) ) is stored in IWORK( 2*I ). The integer IWORK( 2*I-1 ) */
/*     for an unconverged interval is set to the index of the next unconverged */
/*     interval, and is -1 or 0 for a converged interval. Thus a linked */
/*     list of unconverged intervals is set up. */

    i1 = *ifirst;
/*     The number of unconverged intervals */
    nint = 0;
/*     The last unconverged interval found */
    prev = 0;
    rgap = wgap[i1 - *offset];
    i__1 = *ilast;
    for (i__ = i1; i__ <= i__1; ++i__) {
	k = i__ << 1;
	ii = i__ - *offset;
	left = w[ii] - werr[ii];
	right = w[ii] + werr[ii];
	lgap = rgap;
	rgap = wgap[ii];
	gap = f2cmin(lgap,rgap);
/*        Make sure that [LEFT,RIGHT] contains the desired eigenvalue */
/*        Compute negcount from dstqds facto L+D+L+^T = L D L^T - LEFT */

/*        Do while( NEGCNT(LEFT).GT.I-1 ) */

	back = werr[ii];
L20:
	negcnt = dlaneg_(n, &d__[1], &lld[1], &left, pivmin, &r__);
	if (negcnt > i__ - 1) {
	    left -= back;
	    back *= 2.;
	    goto L20;
	}

/*        Do while( NEGCNT(RIGHT).LT.I ) */
/*        Compute negcount from dstqds facto L+D+L+^T = L D L^T - RIGHT */

	back = werr[ii];
L50:
	negcnt = dlaneg_(n, &d__[1], &lld[1], &right, pivmin, &r__);
	if (negcnt < i__) {
	    right += back;
	    back *= 2.;
	    goto L50;
	}
	width = (d__1 = left - right, abs(d__1)) * .5;
/* Computing MAX */
	d__1 = abs(left), d__2 = abs(right);
	tmp = f2cmax(d__1,d__2);
/* Computing MAX */
	d__1 = *rtol1 * gap, d__2 = *rtol2 * tmp;
	cvrgd = f2cmax(d__1,d__2);
	if (width <= cvrgd || width <= mnwdth) {
/*           This interval has already converged and does not need refinement. */
/*           (Note that the gaps might change through refining the */
/*            eigenvalues, however, they can only get bigger.) */
/*           Remove it from the list. */
	    iwork[k - 1] = -1;
/*           Make sure that I1 always points to the first unconverged interval */
	    if (i__ == i1 && i__ < *ilast) {
		i1 = i__ + 1;
	    }
	    if (prev >= i1 && i__ <= *ilast) {
		iwork[(prev << 1) - 1] = i__ + 1;
	    }
	} else {
/*           unconverged interval found */
	    prev = i__;
	    ++nint;
	    iwork[k - 1] = i__ + 1;
	    iwork[k] = negcnt;
	}
	work[k - 1] = left;
	work[k] = right;
/* L75: */
    }

/*     Do while( NINT.GT.0 ), i.e. there are still unconverged intervals */
/*     and while (ITER.LT.MAXITR) */

    iter = 0;
L80:
    prev = i1 - 1;
    i__ = i1;
    olnint = nint;
    i__1 = olnint;
    for (ip = 1; ip <= i__1; ++ip) {
	k = i__ << 1;
	ii = i__ - *offset;
	rgap = wgap[ii];
	lgap = rgap;
	if (ii > 1) {
	    lgap = wgap[ii - 1];
	}
	gap = f2cmin(lgap,rgap);
	next = iwork[k - 1];
	left = work[k - 1];
	right = work[k];
	mid = (left + right) * .5;
/*        semiwidth of interval */
	width = right - mid;
/* Computing MAX */
	d__1 = abs(left), d__2 = abs(right);
	tmp = f2cmax(d__1,d__2);
/* Computing MAX */
	d__1 = *rtol1 * gap, d__2 = *rtol2 * tmp;
	cvrgd = f2cmax(d__1,d__2);
	if (width <= cvrgd || width <= mnwdth || iter == maxitr) {
/*           reduce number of unconverged intervals */
	    --nint;
/*           Mark interval as converged. */
	    iwork[k - 1] = 0;
	    if (i1 == i__) {
		i1 = next;
	    } else {
/*              Prev holds the last unconverged interval previously examined */
		if (prev >= i1) {
		    iwork[(prev << 1) - 1] = next;
		}
	    }
	    i__ = next;
	    goto L100;
	}
	prev = i__;

/*        Perform one bisection step */

	negcnt = dlaneg_(n, &d__[1], &lld[1], &mid, pivmin, &r__);
	if (negcnt <= i__ - 1) {
	    work[k - 1] = mid;
	} else {
	    work[k] = mid;
	}
	i__ = next;
L100:
	;
    }
    ++iter;
/*     do another loop if there are still unconverged intervals */
/*     However, in the last iteration, all intervals are accepted */
/*     since this is the best we can do. */
    if (nint > 0 && iter <= maxitr) {
	goto L80;
    }


/*     At this point, all the intervals have converged */
    i__1 = *ilast;
    for (i__ = *ifirst; i__ <= i__1; ++i__) {
	k = i__ << 1;
	ii = i__ - *offset;
/*        All intervals marked by '0' have been refined. */
	if (iwork[k - 1] == 0) {
	    w[ii] = (work[k - 1] + work[k]) * .5;
	    werr[ii] = work[k] - w[ii];
	}
/* L110: */
    }

    i__1 = *ilast;
    for (i__ = *ifirst + 1; i__ <= i__1; ++i__) {
	k = i__ << 1;
	ii = i__ - *offset;
/* Computing MAX */
	d__1 = 0., d__2 = w[ii] - werr[ii] - w[ii - 1] - werr[ii - 1];
	wgap[ii - 1] = f2cmax(d__1,d__2);
/* L111: */
    }
    return 0;

/*     End of DLARRB */

} /* dlarrb_ */