/* ./src_f77/slaexc.f -- translated by f2c (version 20030320).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include <punc/vf2c.h>

/* Table of constant values */

static integer c__1 = 1;
static integer c__4 = 4;
static logical c_false = FALSE_;
static integer c_n1 = -1;
static integer c__2 = 2;
static integer c__3 = 3;

/* Subroutine */ int slaexc_(logical *wantq, integer *n, real *t, integer *
	ldt, real *q, integer *ldq, integer *j1, integer *n1, integer *n2, 
	real *work, integer *info)
{
    /* System generated locals */
    integer q_dim1, q_offset, t_dim1, t_offset, i__1;
    real r__1, r__2, r__3;

    /* Local variables */
    static real d__[16]	/* was [4][4] */;
    static integer k;
    static real u[3], x[4]	/* was [2][2] */;
    static integer j2, j3, j4;
    static real u1[3], u2[3];
    static integer nd;
    static real cs, t11, t22, t33, sn, wi1, wi2, wr1, wr2, eps, tau, tau1, 
	    tau2;
    static integer ierr;
    static real temp;
    extern /* Subroutine */ int srot_(integer *, real *, integer *, real *, 
	    integer *, real *, real *);
    static real scale, dnorm, xnorm;
    extern /* Subroutine */ int slanv2_(real *, real *, real *, real *, real *
	    , real *, real *, real *, real *, real *), slasy2_(logical *, 
	    logical *, integer *, integer *, integer *, real *, integer *, 
	    real *, integer *, real *, integer *, real *, real *, integer *, 
	    real *, integer *);
    extern doublereal slamch_(char *, ftnlen), slange_(char *, integer *, 
	    integer *, real *, integer *, real *, ftnlen);
    extern /* Subroutine */ int slarfg_(integer *, real *, real *, integer *, 
	    real *), slacpy_(char *, integer *, integer *, real *, integer *, 
	    real *, integer *, ftnlen), slartg_(real *, real *, real *, real *
	    , real *);
    static real thresh;
    extern /* Subroutine */ int slarfx_(char *, integer *, integer *, real *, 
	    real *, real *, integer *, real *, ftnlen);
    static real smlnum;


/*  -- LAPACK auxiliary routine (version 3.0) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/*     Courant Institute, Argonne National Lab, and Rice University */
/*     February 29, 1992 */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  SLAEXC swaps adjacent diagonal blocks T11 and T22 of order 1 or 2 in */
/*  an upper quasi-triangular matrix T by an orthogonal similarity */
/*  transformation. */

/*  T must be in Schur canonical form, that is, block upper triangular */
/*  with 1-by-1 and 2-by-2 diagonal blocks; each 2-by-2 diagonal block */
/*  has its diagonal elemnts equal and its off-diagonal elements of */
/*  opposite sign. */

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

/*  WANTQ   (input) LOGICAL */
/*          = .TRUE. : accumulate the transformation in the matrix Q; */
/*          = .FALSE.: do not accumulate the transformation. */

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

/*  T       (input/output) REAL array, dimension (LDT,N) */
/*          On entry, the upper quasi-triangular matrix T, in Schur */
/*          canonical form. */
/*          On exit, the updated matrix T, again in Schur canonical form. */

/*  LDT     (input)  INTEGER */
/*          The leading dimension of the array T. LDT >= max(1,N). */

/*  Q       (input/output) REAL array, dimension (LDQ,N) */
/*          On entry, if WANTQ is .TRUE., the orthogonal matrix Q. */
/*          On exit, if WANTQ is .TRUE., the updated matrix Q. */
/*          If WANTQ is .FALSE., Q is not referenced. */

/*  LDQ     (input) INTEGER */
/*          The leading dimension of the array Q. */
/*          LDQ >= 1; and if WANTQ is .TRUE., LDQ >= N. */

/*  J1      (input) INTEGER */
/*          The index of the first row of the first block T11. */

/*  N1      (input) INTEGER */
/*          The order of the first block T11. N1 = 0, 1 or 2. */

/*  N2      (input) INTEGER */
/*          The order of the second block T22. N2 = 0, 1 or 2. */

/*  WORK    (workspace) REAL array, dimension (N) */

/*  INFO    (output) INTEGER */
/*          = 0: successful exit */
/*          = 1: the transformed matrix T would be too far from Schur */
/*               form; the blocks are not swapped and T and Q are */
/*               unchanged. */

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

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. Local Arrays .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

    /* Parameter adjustments */
    t_dim1 = *ldt;
    t_offset = 1 + t_dim1;
    t -= t_offset;
    q_dim1 = *ldq;
    q_offset = 1 + q_dim1;
    q -= q_offset;
    --work;

    /* Function Body */
    *info = 0;

/*     Quick return if possible */

    if (*n == 0 || *n1 == 0 || *n2 == 0) {
	return 0;
    }
    if (*j1 + *n1 > *n) {
	return 0;
    }

    j2 = *j1 + 1;
    j3 = *j1 + 2;
    j4 = *j1 + 3;

    if (*n1 == 1 && *n2 == 1) {

/*        Swap two 1-by-1 blocks. */

	t11 = t[*j1 + *j1 * t_dim1];
	t22 = t[j2 + j2 * t_dim1];

/*        Determine the transformation to perform the interchange. */

	r__1 = t22 - t11;
	slartg_(&t[*j1 + j2 * t_dim1], &r__1, &cs, &sn, &temp);

/*        Apply transformation to the matrix T. */

	if (j3 <= *n) {
	    i__1 = *n - *j1 - 1;
	    srot_(&i__1, &t[*j1 + j3 * t_dim1], ldt, &t[j2 + j3 * t_dim1], 
		    ldt, &cs, &sn);
	}
	i__1 = *j1 - 1;
	srot_(&i__1, &t[*j1 * t_dim1 + 1], &c__1, &t[j2 * t_dim1 + 1], &c__1, 
		&cs, &sn);

	t[*j1 + *j1 * t_dim1] = t22;
	t[j2 + j2 * t_dim1] = t11;

	if (*wantq) {

/*           Accumulate transformation in the matrix Q. */

	    srot_(n, &q[*j1 * q_dim1 + 1], &c__1, &q[j2 * q_dim1 + 1], &c__1, 
		    &cs, &sn);
	}

    } else {

/*        Swapping involves at least one 2-by-2 block. */

/*        Copy the diagonal block of order N1+N2 to the local array D */
/*        and compute its norm. */

	nd = *n1 + *n2;
	slacpy_("Full", &nd, &nd, &t[*j1 + *j1 * t_dim1], ldt, d__, &c__4, (
		ftnlen)4);
	dnorm = slange_("Max", &nd, &nd, d__, &c__4, &work[1], (ftnlen)3);

/*        Compute machine-dependent threshold for test for accepting */
/*        swap. */

	eps = slamch_("P", (ftnlen)1);
	smlnum = slamch_("S", (ftnlen)1) / eps;
/* Computing MAX */
	r__1 = eps * 10.f * dnorm;
	thresh = dmax(r__1,smlnum);

/*        Solve T11*X - X*T22 = scale*T12 for X. */

	slasy2_(&c_false, &c_false, &c_n1, n1, n2, d__, &c__4, &d__[*n1 + 1 + 
		(*n1 + 1 << 2) - 5], &c__4, &d__[(*n1 + 1 << 2) - 4], &c__4, &
		scale, x, &c__2, &xnorm, &ierr);

/*        Swap the adjacent diagonal blocks. */

	k = *n1 + *n1 + *n2 - 3;
	switch (k) {
	    case 1:  goto L10;
	    case 2:  goto L20;
	    case 3:  goto L30;
	}

L10:

/*        N1 = 1, N2 = 2: generate elementary reflector H so that: */

/*        ( scale, X11, X12 ) H = ( 0, 0, * ) */

	u[0] = scale;
	u[1] = x[0];
	u[2] = x[2];
	slarfg_(&c__3, &u[2], u, &c__1, &tau);
	u[2] = 1.f;
	t11 = t[*j1 + *j1 * t_dim1];

/*        Perform swap provisionally on diagonal block in D. */

	slarfx_("L", &c__3, &c__3, u, &tau, d__, &c__4, &work[1], (ftnlen)1);
	slarfx_("R", &c__3, &c__3, u, &tau, d__, &c__4, &work[1], (ftnlen)1);

/*        Test whether to reject swap. */

/* Computing MAX */
	r__2 = dabs(d__[2]), r__3 = dabs(d__[6]), r__2 = max(r__2,r__3), r__3 
		= (r__1 = d__[10] - t11, dabs(r__1));
	if (dmax(r__2,r__3) > thresh) {
	    goto L50;
	}

/*        Accept swap: apply transformation to the entire matrix T. */

	i__1 = *n - *j1 + 1;
	slarfx_("L", &c__3, &i__1, u, &tau, &t[*j1 + *j1 * t_dim1], ldt, &
		work[1], (ftnlen)1);
	slarfx_("R", &j2, &c__3, u, &tau, &t[*j1 * t_dim1 + 1], ldt, &work[1],
		 (ftnlen)1);

	t[j3 + *j1 * t_dim1] = 0.f;
	t[j3 + j2 * t_dim1] = 0.f;
	t[j3 + j3 * t_dim1] = t11;

	if (*wantq) {

/*           Accumulate transformation in the matrix Q. */

	    slarfx_("R", n, &c__3, u, &tau, &q[*j1 * q_dim1 + 1], ldq, &work[
		    1], (ftnlen)1);
	}
	goto L40;

L20:

/*        N1 = 2, N2 = 1: generate elementary reflector H so that: */

/*        H (  -X11 ) = ( * ) */
/*          (  -X21 ) = ( 0 ) */
/*          ( scale ) = ( 0 ) */

	u[0] = -x[0];
	u[1] = -x[1];
	u[2] = scale;
	slarfg_(&c__3, u, &u[1], &c__1, &tau);
	u[0] = 1.f;
	t33 = t[j3 + j3 * t_dim1];

/*        Perform swap provisionally on diagonal block in D. */

	slarfx_("L", &c__3, &c__3, u, &tau, d__, &c__4, &work[1], (ftnlen)1);
	slarfx_("R", &c__3, &c__3, u, &tau, d__, &c__4, &work[1], (ftnlen)1);

/*        Test whether to reject swap. */

/* Computing MAX */
	r__2 = dabs(d__[1]), r__3 = dabs(d__[2]), r__2 = max(r__2,r__3), r__3 
		= (r__1 = d__[0] - t33, dabs(r__1));
	if (dmax(r__2,r__3) > thresh) {
	    goto L50;
	}

/*        Accept swap: apply transformation to the entire matrix T. */

	slarfx_("R", &j3, &c__3, u, &tau, &t[*j1 * t_dim1 + 1], ldt, &work[1],
		 (ftnlen)1);
	i__1 = *n - *j1;
	slarfx_("L", &c__3, &i__1, u, &tau, &t[*j1 + j2 * t_dim1], ldt, &work[
		1], (ftnlen)1);

	t[*j1 + *j1 * t_dim1] = t33;
	t[j2 + *j1 * t_dim1] = 0.f;
	t[j3 + *j1 * t_dim1] = 0.f;

	if (*wantq) {

/*           Accumulate transformation in the matrix Q. */

	    slarfx_("R", n, &c__3, u, &tau, &q[*j1 * q_dim1 + 1], ldq, &work[
		    1], (ftnlen)1);
	}
	goto L40;

L30:

/*        N1 = 2, N2 = 2: generate elementary reflectors H(1) and H(2) so */
/*        that: */

/*        H(2) H(1) (  -X11  -X12 ) = (  *  * ) */
/*                  (  -X21  -X22 )   (  0  * ) */
/*                  ( scale    0  )   (  0  0 ) */
/*                  (    0  scale )   (  0  0 ) */

	u1[0] = -x[0];
	u1[1] = -x[1];
	u1[2] = scale;
	slarfg_(&c__3, u1, &u1[1], &c__1, &tau1);
	u1[0] = 1.f;

	temp = -tau1 * (x[2] + u1[1] * x[3]);
	u2[0] = -temp * u1[1] - x[3];
	u2[1] = -temp * u1[2];
	u2[2] = scale;
	slarfg_(&c__3, u2, &u2[1], &c__1, &tau2);
	u2[0] = 1.f;

/*        Perform swap provisionally on diagonal block in D. */

	slarfx_("L", &c__3, &c__4, u1, &tau1, d__, &c__4, &work[1], (ftnlen)1)
		;
	slarfx_("R", &c__4, &c__3, u1, &tau1, d__, &c__4, &work[1], (ftnlen)1)
		;
	slarfx_("L", &c__3, &c__4, u2, &tau2, &d__[1], &c__4, &work[1], (
		ftnlen)1);
	slarfx_("R", &c__4, &c__3, u2, &tau2, &d__[4], &c__4, &work[1], (
		ftnlen)1);

/*        Test whether to reject swap. */

/* Computing MAX */
	r__1 = dabs(d__[2]), r__2 = dabs(d__[6]), r__1 = max(r__1,r__2), r__2 
		= dabs(d__[3]), r__1 = max(r__1,r__2), r__2 = dabs(d__[7]);
	if (dmax(r__1,r__2) > thresh) {
	    goto L50;
	}

/*        Accept swap: apply transformation to the entire matrix T. */

	i__1 = *n - *j1 + 1;
	slarfx_("L", &c__3, &i__1, u1, &tau1, &t[*j1 + *j1 * t_dim1], ldt, &
		work[1], (ftnlen)1);
	slarfx_("R", &j4, &c__3, u1, &tau1, &t[*j1 * t_dim1 + 1], ldt, &work[
		1], (ftnlen)1);
	i__1 = *n - *j1 + 1;
	slarfx_("L", &c__3, &i__1, u2, &tau2, &t[j2 + *j1 * t_dim1], ldt, &
		work[1], (ftnlen)1);
	slarfx_("R", &j4, &c__3, u2, &tau2, &t[j2 * t_dim1 + 1], ldt, &work[1]
		, (ftnlen)1);

	t[j3 + *j1 * t_dim1] = 0.f;
	t[j3 + j2 * t_dim1] = 0.f;
	t[j4 + *j1 * t_dim1] = 0.f;
	t[j4 + j2 * t_dim1] = 0.f;

	if (*wantq) {

/*           Accumulate transformation in the matrix Q. */

	    slarfx_("R", n, &c__3, u1, &tau1, &q[*j1 * q_dim1 + 1], ldq, &
		    work[1], (ftnlen)1);
	    slarfx_("R", n, &c__3, u2, &tau2, &q[j2 * q_dim1 + 1], ldq, &work[
		    1], (ftnlen)1);
	}

L40:

	if (*n2 == 2) {

/*           Standardize new 2-by-2 block T11 */

	    slanv2_(&t[*j1 + *j1 * t_dim1], &t[*j1 + j2 * t_dim1], &t[j2 + *
		    j1 * t_dim1], &t[j2 + j2 * t_dim1], &wr1, &wi1, &wr2, &
		    wi2, &cs, &sn);
	    i__1 = *n - *j1 - 1;
	    srot_(&i__1, &t[*j1 + (*j1 + 2) * t_dim1], ldt, &t[j2 + (*j1 + 2) 
		    * t_dim1], ldt, &cs, &sn);
	    i__1 = *j1 - 1;
	    srot_(&i__1, &t[*j1 * t_dim1 + 1], &c__1, &t[j2 * t_dim1 + 1], &
		    c__1, &cs, &sn);
	    if (*wantq) {
		srot_(n, &q[*j1 * q_dim1 + 1], &c__1, &q[j2 * q_dim1 + 1], &
			c__1, &cs, &sn);
	    }
	}

	if (*n1 == 2) {

/*           Standardize new 2-by-2 block T22 */

	    j3 = *j1 + *n2;
	    j4 = j3 + 1;
	    slanv2_(&t[j3 + j3 * t_dim1], &t[j3 + j4 * t_dim1], &t[j4 + j3 * 
		    t_dim1], &t[j4 + j4 * t_dim1], &wr1, &wi1, &wr2, &wi2, &
		    cs, &sn);
	    if (j3 + 2 <= *n) {
		i__1 = *n - j3 - 1;
		srot_(&i__1, &t[j3 + (j3 + 2) * t_dim1], ldt, &t[j4 + (j3 + 2)
			 * t_dim1], ldt, &cs, &sn);
	    }
	    i__1 = j3 - 1;
	    srot_(&i__1, &t[j3 * t_dim1 + 1], &c__1, &t[j4 * t_dim1 + 1], &
		    c__1, &cs, &sn);
	    if (*wantq) {
		srot_(n, &q[j3 * q_dim1 + 1], &c__1, &q[j4 * q_dim1 + 1], &
			c__1, &cs, &sn);
	    }
	}

    }
    return 0;

/*     Exit with INFO = 1 if swap was rejected. */

L50:
    *info = 1;
    return 0;

/*     End of SLAEXC */

} /* slaexc_ */

