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

/* Subroutine */ int zhsein_(char *side, char *eigsrc, char *initv, logical *
	select, integer *n, doublecomplex *h__, integer *ldh, doublecomplex *
	w, doublecomplex *vl, integer *ldvl, doublecomplex *vr, integer *ldvr,
	 integer *mm, integer *m, doublecomplex *work, doublereal *rwork, 
	integer *ifaill, integer *ifailr, integer *info)
{
/*  -- LAPACK routine (version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       September 30, 1994   


    Purpose   
    =======   

    ZHSEIN uses inverse iteration to find specified right and/or left   
    eigenvectors of a complex upper Hessenberg matrix H.   

    The right eigenvector x and the left eigenvector y of the matrix H   
    corresponding to an eigenvalue w are defined by:   

                 H * x = w * x,     y**h * H = w * y**h   

    where y**h denotes the conjugate transpose of the vector y.   

    Arguments   
    =========   

    SIDE    (input) CHARACTER*1   
            = 'R': compute right eigenvectors only;   
            = 'L': compute left eigenvectors only;   
            = 'B': compute both right and left eigenvectors.   

    EIGSRC  (input) CHARACTER*1   
            Specifies the source of eigenvalues supplied in W:   
            = 'Q': the eigenvalues were found using ZHSEQR; thus, if   
                   H has zero subdiagonal elements, and so is   
                   block-triangular, then the j-th eigenvalue can be   
                   assumed to be an eigenvalue of the block containing   
                   the j-th row/column.  This property allows ZHSEIN to   
                   perform inverse iteration on just one diagonal block.   
            = 'N': no assumptions are made on the correspondence   
                   between eigenvalues and diagonal blocks.  In this   
                   case, ZHSEIN must always perform inverse iteration   
                   using the whole matrix H.   

    INITV   (input) CHARACTER*1   
            = 'N': no initial vectors are supplied;   
            = 'U': user-supplied initial vectors are stored in the arrays   
                   VL and/or VR.   

    SELECT  (input) LOGICAL array, dimension (N)   
            Specifies the eigenvectors to be computed. To select the   
            eigenvector corresponding to the eigenvalue W(j),   
            SELECT(j) must be set to .TRUE..   

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

    H       (input) COMPLEX*16 array, dimension (LDH,N)   
            The upper Hessenberg matrix H.   

    LDH     (input) INTEGER   
            The leading dimension of the array H.  LDH >= max(1,N).   

    W       (input/output) COMPLEX*16 array, dimension (N)   
            On entry, the eigenvalues of H.   
            On exit, the real parts of W may have been altered since   
            close eigenvalues are perturbed slightly in searching for   
            independent eigenvectors.   

    VL      (input/output) COMPLEX*16 array, dimension (LDVL,MM)   
            On entry, if INITV = 'U' and SIDE = 'L' or 'B', VL must   
            contain starting vectors for the inverse iteration for the   
            left eigenvectors; the starting vector for each eigenvector   
            must be in the same column in which the eigenvector will be   
            stored.   
            On exit, if SIDE = 'L' or 'B', the left eigenvectors   
            specified by SELECT will be stored consecutively in the   
            columns of VL, in the same order as their eigenvalues.   
            If SIDE = 'R', VL is not referenced.   

    LDVL    (input) INTEGER   
            The leading dimension of the array VL.   
            LDVL >= max(1,N) if SIDE = 'L' or 'B'; LDVL >= 1 otherwise.   

    VR      (input/output) COMPLEX*16 array, dimension (LDVR,MM)   
            On entry, if INITV = 'U' and SIDE = 'R' or 'B', VR must   
            contain starting vectors for the inverse iteration for the   
            right eigenvectors; the starting vector for each eigenvector   
            must be in the same column in which the eigenvector will be   
            stored.   
            On exit, if SIDE = 'R' or 'B', the right eigenvectors   
            specified by SELECT will be stored consecutively in the   
            columns of VR, in the same order as their eigenvalues.   
            If SIDE = 'L', VR is not referenced.   

    LDVR    (input) INTEGER   
            The leading dimension of the array VR.   
            LDVR >= max(1,N) if SIDE = 'R' or 'B'; LDVR >= 1 otherwise.   

    MM      (input) INTEGER   
            The number of columns in the arrays VL and/or VR. MM >= M.   

    M       (output) INTEGER   
            The number of columns in the arrays VL and/or VR required to   
            store the eigenvectors (= the number of .TRUE. elements in   
            SELECT).   

    WORK    (workspace) COMPLEX*16 array, dimension (N*N)   

    RWORK   (workspace) DOUBLE PRECISION array, dimension (N)   

    IFAILL  (output) INTEGER array, dimension (MM)   
            If SIDE = 'L' or 'B', IFAILL(i) = j > 0 if the left   
            eigenvector in the i-th column of VL (corresponding to the   
            eigenvalue w(j)) failed to converge; IFAILL(i) = 0 if the   
            eigenvector converged satisfactorily.   
            If SIDE = 'R', IFAILL is not referenced.   

    IFAILR  (output) INTEGER array, dimension (MM)   
            If SIDE = 'R' or 'B', IFAILR(i) = j > 0 if the right   
            eigenvector in the i-th column of VR (corresponding to the   
            eigenvalue w(j)) failed to converge; IFAILR(i) = 0 if the   
            eigenvector converged satisfactorily.   
            If SIDE = 'L', IFAILR is not referenced.   

    INFO    (output) INTEGER   
            = 0:  successful exit   
            < 0:  if INFO = -i, the i-th argument had an illegal value   
            > 0:  if INFO = i, i is the number of eigenvectors which   
                  failed to converge; see IFAILL and IFAILR for further   
                  details.   

    Further Details   
    ===============   

    Each eigenvector is normalized so that the element of largest   
    magnitude has magnitude 1; here the magnitude of a complex number   
    (x,y) is taken to be |x|+|y|.   

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


       Decode and test the input parameters.   

       Parameter adjustments */
    /* Table of constant values */
    static logical c_false = FALSE_;
    static logical c_true = TRUE_;
    
    /* System generated locals */
    integer h_dim1, h_offset, vl_dim1, vl_offset, vr_dim1, vr_offset, i__1, 
	    i__2, i__3;
    doublereal d__1, d__2;
    doublecomplex z__1, z__2;
    /* Builtin functions */
    double d_imag(doublecomplex *);
    /* Local variables */
    static doublereal unfl;
    static integer i__, k;
    extern logical lsame_(char *, char *);
    static integer iinfo;
    static logical leftv, bothv;
    static doublereal hnorm;
    static integer kl;
    extern doublereal dlamch_(char *);
    static integer kr, ks;
    static doublecomplex wk;
    extern /* Subroutine */ int xerbla_(char *, integer *), zlaein_(
	    logical *, logical *, integer *, doublecomplex *, integer *, 
	    doublecomplex *, doublecomplex *, doublecomplex *, integer *, 
	    doublereal *, doublereal *, doublereal *, integer *);
    extern doublereal zlanhs_(char *, integer *, doublecomplex *, integer *, 
	    doublereal *);
    static logical noinit;
    static integer ldwork;
    static logical rightv, fromqr;
    static doublereal smlnum;
    static integer kln;
    static doublereal ulp, eps3;
#define h___subscr(a_1,a_2) (a_2)*h_dim1 + a_1
#define h___ref(a_1,a_2) h__[h___subscr(a_1,a_2)]
#define vl_subscr(a_1,a_2) (a_2)*vl_dim1 + a_1
#define vl_ref(a_1,a_2) vl[vl_subscr(a_1,a_2)]
#define vr_subscr(a_1,a_2) (a_2)*vr_dim1 + a_1
#define vr_ref(a_1,a_2) vr[vr_subscr(a_1,a_2)]


    --select;
    h_dim1 = *ldh;
    h_offset = 1 + h_dim1 * 1;
    h__ -= h_offset;
    --w;
    vl_dim1 = *ldvl;
    vl_offset = 1 + vl_dim1 * 1;
    vl -= vl_offset;
    vr_dim1 = *ldvr;
    vr_offset = 1 + vr_dim1 * 1;
    vr -= vr_offset;
    --work;
    --rwork;
    --ifaill;
    --ifailr;

    /* Function Body */
    bothv = lsame_(side, "B");
    rightv = lsame_(side, "R") || bothv;
    leftv = lsame_(side, "L") || bothv;

    fromqr = lsame_(eigsrc, "Q");

    noinit = lsame_(initv, "N");

/*     Set M to the number of columns required to store the selected   
       eigenvectors. */

    *m = 0;
    i__1 = *n;
    for (k = 1; k <= i__1; ++k) {
	if (select[k]) {
	    ++(*m);
	}
/* L10: */
    }

    *info = 0;
    if (! rightv && ! leftv) {
	*info = -1;
    } else if (! fromqr && ! lsame_(eigsrc, "N")) {
	*info = -2;
    } else if (! noinit && ! lsame_(initv, "U")) {
	*info = -3;
    } else if (*n < 0) {
	*info = -5;
    } else if (*ldh < max(1,*n)) {
	*info = -7;
    } else if (*ldvl < 1 || leftv && *ldvl < *n) {
	*info = -10;
    } else if (*ldvr < 1 || rightv && *ldvr < *n) {
	*info = -12;
    } else if (*mm < *m) {
	*info = -13;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("ZHSEIN", &i__1);
	return 0;
    }

/*     Quick return if possible. */

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

/*     Set machine-dependent constants. */

    unfl = dlamch_("Safe minimum");
    ulp = dlamch_("Precision");
    smlnum = unfl * (*n / ulp);

    ldwork = *n;

    kl = 1;
    kln = 0;
    if (fromqr) {
	kr = 0;
    } else {
	kr = *n;
    }
    ks = 1;

    i__1 = *n;
    for (k = 1; k <= i__1; ++k) {
	if (select[k]) {

/*           Compute eigenvector(s) corresponding to W(K). */

	    if (fromqr) {

/*              If affiliation of eigenvalues is known, check whether   
                the matrix splits.   

                Determine KL and KR such that 1 <= KL <= K <= KR <= N   
                and H(KL,KL-1) and H(KR+1,KR) are zero (or KL = 1 or   
                KR = N).   

                Then inverse iteration can be performed with the   
                submatrix H(KL:N,KL:N) for a left eigenvector, and with   
                the submatrix H(1:KR,1:KR) for a right eigenvector. */

		i__2 = kl + 1;
		for (i__ = k; i__ >= i__2; --i__) {
		    i__3 = h___subscr(i__, i__ - 1);
		    if (h__[i__3].r == 0. && h__[i__3].i == 0.) {
			goto L30;
		    }
/* L20: */
		}
L30:
		kl = i__;
		if (k > kr) {
		    i__2 = *n - 1;
		    for (i__ = k; i__ <= i__2; ++i__) {
			i__3 = h___subscr(i__ + 1, i__);
			if (h__[i__3].r == 0. && h__[i__3].i == 0.) {
			    goto L50;
			}
/* L40: */
		    }
L50:
		    kr = i__;
		}
	    }

	    if (kl != kln) {
		kln = kl;

/*              Compute infinity-norm of submatrix H(KL:KR,KL:KR) if it   
                has not ben computed before. */

		i__2 = kr - kl + 1;
		hnorm = zlanhs_("I", &i__2, &h___ref(kl, kl), ldh, &rwork[1]);
		if (hnorm > 0.) {
		    eps3 = hnorm * ulp;
		} else {
		    eps3 = smlnum;
		}
	    }

/*           Perturb eigenvalue if it is close to any previous   
             selected eigenvalues affiliated to the submatrix   
             H(KL:KR,KL:KR). Close roots are modified by EPS3. */

	    i__2 = k;
	    wk.r = w[i__2].r, wk.i = w[i__2].i;
L60:
	    i__2 = kl;
	    for (i__ = k - 1; i__ >= i__2; --i__) {
		i__3 = i__;
		z__2.r = w[i__3].r - wk.r, z__2.i = w[i__3].i - wk.i;
		z__1.r = z__2.r, z__1.i = z__2.i;
		if (select[i__] && (d__1 = z__1.r, abs(d__1)) + (d__2 = 
			d_imag(&z__1), abs(d__2)) < eps3) {
		    z__1.r = wk.r + eps3, z__1.i = wk.i;
		    wk.r = z__1.r, wk.i = z__1.i;
		    goto L60;
		}
/* L70: */
	    }
	    i__2 = k;
	    w[i__2].r = wk.r, w[i__2].i = wk.i;

	    if (leftv) {

/*              Compute left eigenvector. */

		i__2 = *n - kl + 1;
		zlaein_(&c_false, &noinit, &i__2, &h___ref(kl, kl), ldh, &wk, 
			&vl_ref(kl, ks), &work[1], &ldwork, &rwork[1], &eps3, 
			&smlnum, &iinfo);
		if (iinfo > 0) {
		    ++(*info);
		    ifaill[ks] = k;
		} else {
		    ifaill[ks] = 0;
		}
		i__2 = kl - 1;
		for (i__ = 1; i__ <= i__2; ++i__) {
		    i__3 = vl_subscr(i__, ks);
		    vl[i__3].r = 0., vl[i__3].i = 0.;
/* L80: */
		}
	    }
	    if (rightv) {

/*              Compute right eigenvector. */

		zlaein_(&c_true, &noinit, &kr, &h__[h_offset], ldh, &wk, &
			vr_ref(1, ks), &work[1], &ldwork, &rwork[1], &eps3, &
			smlnum, &iinfo);
		if (iinfo > 0) {
		    ++(*info);
		    ifailr[ks] = k;
		} else {
		    ifailr[ks] = 0;
		}
		i__2 = *n;
		for (i__ = kr + 1; i__ <= i__2; ++i__) {
		    i__3 = vr_subscr(i__, ks);
		    vr[i__3].r = 0., vr[i__3].i = 0.;
/* L90: */
		}
	    }
	    ++ks;
	}
/* L100: */
    }

    return 0;

/*     End of ZHSEIN */

} /* zhsein_ */

#undef vr_ref
#undef vr_subscr
#undef vl_ref
#undef vl_subscr
#undef h___ref
#undef h___subscr


