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

/* Subroutine */ int stgexc_(logical *wantq, logical *wantz, integer *n, real 
	*a, integer *lda, real *b, integer *ldb, real *q, integer *ldq, real *
	z__, integer *ldz, integer *ifst, integer *ilst, real *work, integer *
	lwork, integer *info)
{
/*  -- LAPACK routine (version 3.1) --   
       Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..   
       November 2006   


    Purpose   
    =======   

    STGEXC reorders the generalized real Schur decomposition of a real   
    matrix pair (A,B) using an orthogonal equivalence transformation   

                   (A, B) = Q * (A, B) * Z',   

    so that the diagonal block of (A, B) with row index IFST is moved   
    to row ILST.   

    (A, B) must be in generalized real Schur canonical form (as returned   
    by SGGES), i.e. A is block upper triangular with 1-by-1 and 2-by-2   
    diagonal blocks. B is upper triangular.   

    Optionally, the matrices Q and Z of generalized Schur vectors are   
    updated.   

           Q(in) * A(in) * Z(in)' = Q(out) * A(out) * Z(out)'   
           Q(in) * B(in) * Z(in)' = Q(out) * B(out) * Z(out)'   


    Arguments   
    =========   

    WANTQ   (input) LOGICAL   
            .TRUE. : update the left transformation matrix Q;   
            .FALSE.: do not update Q.   

    WANTZ   (input) LOGICAL   
            .TRUE. : update the right transformation matrix Z;   
            .FALSE.: do not update Z.   

    N       (input) INTEGER   
            The order of the matrices A and B. N >= 0.   

    A       (input/output) REAL array, dimension (LDA,N)   
            On entry, the matrix A in generalized real Schur canonical   
            form.   
            On exit, the updated matrix A, again in generalized   
            real Schur canonical form.   

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

    B       (input/output) REAL array, dimension (LDB,N)   
            On entry, the matrix B in generalized real Schur canonical   
            form (A,B).   
            On exit, the updated matrix B, again in generalized   
            real Schur canonical form (A,B).   

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

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

    LDQ     (input) INTEGER   
            The leading dimension of the array Q. LDQ >= 1.   
            If WANTQ = .TRUE., LDQ >= N.   

    Z       (input/output) REAL array, dimension (LDZ,N)   
            On entry, if WANTZ = .TRUE., the orthogonal matrix Z.   
            On exit, the updated matrix Z.   
            If WANTZ = .FALSE., Z is not referenced.   

    LDZ     (input) INTEGER   
            The leading dimension of the array Z. LDZ >= 1.   
            If WANTZ = .TRUE., LDZ >= N.   

    IFST    (input/output) INTEGER   
    ILST    (input/output) INTEGER   
            Specify the reordering of the diagonal blocks of (A, B).   
            The block with row index IFST is moved to row ILST, by a   
            sequence of swapping between adjacent blocks.   
            On exit, if IFST pointed on entry to the second row of   
            a 2-by-2 block, it is changed to point to the first row;   
            ILST always points to the first row of the block in its   
            final position (which may differ from its input value by   
            +1 or -1). 1 <= IFST, ILST <= N.   

    WORK    (workspace/output) REAL array, dimension (MAX(1,LWORK))   
            On exit, if INFO = 0, WORK(1) returns the optimal LWORK.   

    LWORK   (input) INTEGER   
            The dimension of the array WORK.   
            LWORK >= 1 when N <= 1, otherwise LWORK >= 4*N + 16.   

            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.   

    INFO    (output) INTEGER   
             =0:  successful exit.   
             <0:  if INFO = -i, the i-th argument had an illegal value.   
             =1:  The transformed matrix pair (A, B) would be too far   
                  from generalized Schur form; the problem is ill-   
                  conditioned. (A, B) may have been partially reordered,   
                  and ILST points to the first row of the current   
                  position of the block being moved.   

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

    Based on contributions by   
       Bo Kagstrom and Peter Poromaa, Department of Computing Science,   
       Umea University, S-901 87 Umea, Sweden.   

    [1] B. Kagstrom; A Direct Method for Reordering Eigenvalues in the   
        Generalized Real Schur Form of a Regular Matrix Pair (A, B), in   
        M.S. Moonen et al (eds), Linear Algebra for Large Scale and   
        Real-Time Applications, Kluwer Academic Publ. 1993, pp 195-218.   

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


       Decode and test input arguments.   

       Parameter adjustments */
    /* Table of constant values */
    static integer c__1 = 1;
    static integer c__2 = 2;
    
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, q_dim1, q_offset, z_dim1, 
	    z_offset, i__1;
    /* Local variables */
    static integer nbf, nbl, here, lwmin;
    extern /* Subroutine */ int stgex2_(logical *, logical *, integer *, real 
	    *, integer *, real *, integer *, real *, integer *, real *, 
	    integer *, integer *, integer *, integer *, real *, integer *, 
	    integer *), xerbla_(char *, integer *);
    static integer nbnext;
    static logical lquery;


    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;
    q_dim1 = *ldq;
    q_offset = 1 + q_dim1;
    q -= q_offset;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1;
    z__ -= z_offset;
    --work;

    /* Function Body */
    *info = 0;
    lquery = *lwork == -1;
    if (*n < 0) {
	*info = -3;
    } else if (*lda < max(1,*n)) {
	*info = -5;
    } else if (*ldb < max(1,*n)) {
	*info = -7;
    } else if (*ldq < 1 || *wantq && *ldq < max(1,*n)) {
	*info = -9;
    } else if (*ldz < 1 || *wantz && *ldz < max(1,*n)) {
	*info = -11;
    } else if (*ifst < 1 || *ifst > *n) {
	*info = -12;
    } else if (*ilst < 1 || *ilst > *n) {
	*info = -13;
    }

    if (*info == 0) {
	if (*n <= 1) {
	    lwmin = 1;
	} else {
	    lwmin = (*n << 2) + 16;
	}
	work[1] = (real) lwmin;

	if (*lwork < lwmin && ! lquery) {
	    *info = -15;
	}
    }

    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("STGEXC", &i__1);
	return 0;
    } else if (lquery) {
	return 0;
    }

/*     Quick return if possible */

    if (*n <= 1) {
	return 0;
    }

/*     Determine the first row of the specified block and find out   
       if it is 1-by-1 or 2-by-2. */

    if (*ifst > 1) {
	if (a[*ifst + (*ifst - 1) * a_dim1] != 0.f) {
	    --(*ifst);
	}
    }
    nbf = 1;
    if (*ifst < *n) {
	if (a[*ifst + 1 + *ifst * a_dim1] != 0.f) {
	    nbf = 2;
	}
    }

/*     Determine the first row of the final block   
       and find out if it is 1-by-1 or 2-by-2. */

    if (*ilst > 1) {
	if (a[*ilst + (*ilst - 1) * a_dim1] != 0.f) {
	    --(*ilst);
	}
    }
    nbl = 1;
    if (*ilst < *n) {
	if (a[*ilst + 1 + *ilst * a_dim1] != 0.f) {
	    nbl = 2;
	}
    }
    if (*ifst == *ilst) {
	return 0;
    }

    if (*ifst < *ilst) {

/*        Update ILST. */

	if (nbf == 2 && nbl == 1) {
	    --(*ilst);
	}
	if (nbf == 1 && nbl == 2) {
	    ++(*ilst);
	}

	here = *ifst;

L10:

/*        Swap with next one below. */

	if (nbf == 1 || nbf == 2) {

/*           Current block either 1-by-1 or 2-by-2. */

	    nbnext = 1;
	    if (here + nbf + 1 <= *n) {
		if (a[here + nbf + 1 + (here + nbf) * a_dim1] != 0.f) {
		    nbnext = 2;
		}
	    }
	    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb, &q[
		    q_offset], ldq, &z__[z_offset], ldz, &here, &nbf, &nbnext,
		     &work[1], lwork, info);
	    if (*info != 0) {
		*ilst = here;
		return 0;
	    }
	    here += nbnext;

/*           Test if 2-by-2 block breaks into two 1-by-1 blocks. */

	    if (nbf == 2) {
		if (a[here + 1 + here * a_dim1] == 0.f) {
		    nbf = 3;
		}
	    }

	} else {

/*           Current block consists of two 1-by-1 blocks, each of which   
             must be swapped individually. */

	    nbnext = 1;
	    if (here + 3 <= *n) {
		if (a[here + 3 + (here + 2) * a_dim1] != 0.f) {
		    nbnext = 2;
		}
	    }
	    i__1 = here + 1;
	    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb, &q[
		    q_offset], ldq, &z__[z_offset], ldz, &i__1, &c__1, &
		    nbnext, &work[1], lwork, info);
	    if (*info != 0) {
		*ilst = here;
		return 0;
	    }
	    if (nbnext == 1) {

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

		stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb,
			 &q[q_offset], ldq, &z__[z_offset], ldz, &here, &c__1,
			 &c__1, &work[1], lwork, info);
		if (*info != 0) {
		    *ilst = here;
		    return 0;
		}
		++here;

	    } else {

/*              Recompute NBNEXT in case of 2-by-2 split. */

		if (a[here + 2 + (here + 1) * a_dim1] == 0.f) {
		    nbnext = 1;
		}
		if (nbnext == 2) {

/*                 2-by-2 block did not split. */

		    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], 
			    ldb, &q[q_offset], ldq, &z__[z_offset], ldz, &
			    here, &c__1, &nbnext, &work[1], lwork, info);
		    if (*info != 0) {
			*ilst = here;
			return 0;
		    }
		    here += 2;
		} else {

/*                 2-by-2 block did split. */

		    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], 
			    ldb, &q[q_offset], ldq, &z__[z_offset], ldz, &
			    here, &c__1, &c__1, &work[1], lwork, info);
		    if (*info != 0) {
			*ilst = here;
			return 0;
		    }
		    ++here;
		    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], 
			    ldb, &q[q_offset], ldq, &z__[z_offset], ldz, &
			    here, &c__1, &c__1, &work[1], lwork, info);
		    if (*info != 0) {
			*ilst = here;
			return 0;
		    }
		    ++here;
		}

	    }
	}
	if (here < *ilst) {
	    goto L10;
	}
    } else {
	here = *ifst;

L20:

/*        Swap with next one below. */

	if (nbf == 1 || nbf == 2) {

/*           Current block either 1-by-1 or 2-by-2. */

	    nbnext = 1;
	    if (here >= 3) {
		if (a[here - 1 + (here - 2) * a_dim1] != 0.f) {
		    nbnext = 2;
		}
	    }
	    i__1 = here - nbnext;
	    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb, &q[
		    q_offset], ldq, &z__[z_offset], ldz, &i__1, &nbnext, &nbf,
		     &work[1], lwork, info);
	    if (*info != 0) {
		*ilst = here;
		return 0;
	    }
	    here -= nbnext;

/*           Test if 2-by-2 block breaks into two 1-by-1 blocks. */

	    if (nbf == 2) {
		if (a[here + 1 + here * a_dim1] == 0.f) {
		    nbf = 3;
		}
	    }

	} else {

/*           Current block consists of two 1-by-1 blocks, each of which   
             must be swapped individually. */

	    nbnext = 1;
	    if (here >= 3) {
		if (a[here - 1 + (here - 2) * a_dim1] != 0.f) {
		    nbnext = 2;
		}
	    }
	    i__1 = here - nbnext;
	    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb, &q[
		    q_offset], ldq, &z__[z_offset], ldz, &i__1, &nbnext, &
		    c__1, &work[1], lwork, info);
	    if (*info != 0) {
		*ilst = here;
		return 0;
	    }
	    if (nbnext == 1) {

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

		stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb,
			 &q[q_offset], ldq, &z__[z_offset], ldz, &here, &
			nbnext, &c__1, &work[1], lwork, info);
		if (*info != 0) {
		    *ilst = here;
		    return 0;
		}
		--here;
	    } else {

/*             Recompute NBNEXT in case of 2-by-2 split. */

		if (a[here + (here - 1) * a_dim1] == 0.f) {
		    nbnext = 1;
		}
		if (nbnext == 2) {

/*                 2-by-2 block did not split. */

		    i__1 = here - 1;
		    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], 
			    ldb, &q[q_offset], ldq, &z__[z_offset], ldz, &
			    i__1, &c__2, &c__1, &work[1], lwork, info);
		    if (*info != 0) {
			*ilst = here;
			return 0;
		    }
		    here += -2;
		} else {

/*                 2-by-2 block did split. */

		    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], 
			    ldb, &q[q_offset], ldq, &z__[z_offset], ldz, &
			    here, &c__1, &c__1, &work[1], lwork, info);
		    if (*info != 0) {
			*ilst = here;
			return 0;
		    }
		    --here;
		    stgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], 
			    ldb, &q[q_offset], ldq, &z__[z_offset], ldz, &
			    here, &c__1, &c__1, &work[1], lwork, info);
		    if (*info != 0) {
			*ilst = here;
			return 0;
		    }
		    --here;
		}
	    }
	}
	if (here > *ilst) {
	    goto L20;
	}
    }
    *ilst = here;
    work[1] = (real) lwmin;
    return 0;

/*     End of STGEXC */

} /* stgexc_ */