/* dtgsna.f -- translated by f2c (version 20061008).
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"
#include "blaswrap.h"
/* Table of constant values */
static integer c__1 = 1;
static doublereal c_b19 = 1.;
static doublereal c_b21 = 0.;
static integer c__2 = 2;
static logical c_false = FALSE_;
static integer c__3 = 3;
/* Subroutine */ int dtgsna_(char *job, char *howmny, logical *select,
integer *n, doublereal *a, integer *lda, doublereal *b, integer *ldb,
doublereal *vl, integer *ldvl, doublereal *vr, integer *ldvr,
doublereal *s, doublereal *dif, integer *mm, integer *m, doublereal *
work, integer *lwork, integer *iwork, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, b_dim1, b_offset, vl_dim1, vl_offset, vr_dim1,
vr_offset, i__1, i__2;
doublereal d__1, d__2;
/* Builtin functions */
double sqrt(doublereal);
/* Local variables */
integer i__, k;
doublereal c1, c2;
integer n1, n2, ks, iz;
doublereal eps, beta, cond;
extern doublereal ddot_(integer *, doublereal *, integer *, doublereal *,
integer *);
logical pair;
integer ierr;
doublereal uhav, uhbv;
integer ifst;
doublereal lnrm;
integer ilst;
doublereal rnrm;
extern /* Subroutine */ int dlag2_(doublereal *, integer *, doublereal *,
integer *, doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *, doublereal *);
extern doublereal dnrm2_(integer *, doublereal *, integer *);
doublereal root1, root2, scale;
extern logical lsame_(char *, char *);
extern /* Subroutine */ int dgemv_(char *, integer *, integer *,
doublereal *, doublereal *, integer *, doublereal *, integer *,
doublereal *, doublereal *, integer *);
doublereal uhavi, uhbvi, tmpii;
integer lwmin;
logical wants;
doublereal tmpir, tmpri, dummy[1], tmprr;
extern doublereal dlapy2_(doublereal *, doublereal *);
doublereal dummy1[1];
extern doublereal dlamch_(char *);
doublereal alphai, alphar;
extern /* Subroutine */ int dlacpy_(char *, integer *, integer *,
doublereal *, integer *, doublereal *, integer *),
xerbla_(char *, integer *), dtgexc_(logical *, logical *,
integer *, doublereal *, integer *, doublereal *, integer *,
doublereal *, integer *, doublereal *, integer *, integer *,
integer *, doublereal *, integer *, integer *);
logical wantbh, wantdf, somcon;
doublereal alprqt;
extern /* Subroutine */ int dtgsyl_(char *, integer *, integer *, integer
*, doublereal *, integer *, doublereal *, integer *, doublereal *,
integer *, doublereal *, integer *, doublereal *, integer *,
doublereal *, integer *, doublereal *, doublereal *, doublereal *,
integer *, integer *, integer *);
doublereal smlnum;
logical lquery;
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DTGSNA estimates reciprocal condition numbers for specified */
/* eigenvalues and/or eigenvectors of a matrix pair (A, B) in */
/* generalized real Schur canonical form (or of any matrix pair */
/* (Q*A*Z', Q*B*Z') with orthogonal matrices Q and Z, where */
/* Z' denotes the transpose of Z. */
/* (A, B) must be in generalized real Schur form (as returned by DGGES), */
/* i.e. A is block upper triangular with 1-by-1 and 2-by-2 diagonal */
/* blocks. B is upper triangular. */
/* Arguments */
/* ========= */
/* JOB (input) CHARACTER*1 */
/* Specifies whether condition numbers are required for */
/* eigenvalues (S) or eigenvectors (DIF): */
/* = 'E': for eigenvalues only (S); */
/* = 'V': for eigenvectors only (DIF); */
/* = 'B': for both eigenvalues and eigenvectors (S and DIF). */
/* HOWMNY (input) CHARACTER*1 */
/* = 'A': compute condition numbers for all eigenpairs; */
/* = 'S': compute condition numbers for selected eigenpairs */
/* specified by the array SELECT. */
/* SELECT (input) LOGICAL array, dimension (N) */
/* If HOWMNY = 'S', SELECT specifies the eigenpairs for which */
/* condition numbers are required. To select condition numbers */
/* for the eigenpair corresponding to a real eigenvalue w(j), */
/* SELECT(j) must be set to .TRUE.. To select condition numbers */
/* corresponding to a complex conjugate pair of eigenvalues w(j) */
/* and w(j+1), either SELECT(j) or SELECT(j+1) or both, must be */
/* set to .TRUE.. */
/* If HOWMNY = 'A', SELECT is not referenced. */
/* N (input) INTEGER */
/* The order of the square matrix pair (A, B). N >= 0. */
/* A (input) DOUBLE PRECISION array, dimension (LDA,N) */
/* The upper quasi-triangular matrix A in the pair (A,B). */
/* LDA (input) INTEGER */
/* The leading dimension of the array A. LDA >= max(1,N). */
/* B (input) DOUBLE PRECISION array, dimension (LDB,N) */
/* The upper triangular matrix B in the pair (A,B). */
/* LDB (input) INTEGER */
/* The leading dimension of the array B. LDB >= max(1,N). */
/* VL (input) DOUBLE PRECISION array, dimension (LDVL,M) */
/* If JOB = 'E' or 'B', VL must contain left eigenvectors of */
/* (A, B), corresponding to the eigenpairs specified by HOWMNY */
/* and SELECT. The eigenvectors must be stored in consecutive */
/* columns of VL, as returned by DTGEVC. */
/* If JOB = 'V', VL is not referenced. */
/* LDVL (input) INTEGER */
/* The leading dimension of the array VL. LDVL >= 1. */
/* If JOB = 'E' or 'B', LDVL >= N. */
/* VR (input) DOUBLE PRECISION array, dimension (LDVR,M) */
/* If JOB = 'E' or 'B', VR must contain right eigenvectors of */
/* (A, B), corresponding to the eigenpairs specified by HOWMNY */
/* and SELECT. The eigenvectors must be stored in consecutive */
/* columns ov VR, as returned by DTGEVC. */
/* If JOB = 'V', VR is not referenced. */
/* LDVR (input) INTEGER */
/* The leading dimension of the array VR. LDVR >= 1. */
/* If JOB = 'E' or 'B', LDVR >= N. */
/* S (output) DOUBLE PRECISION array, dimension (MM) */
/* If JOB = 'E' or 'B', the reciprocal condition numbers of the */
/* selected eigenvalues, stored in consecutive elements of the */
/* array. For a complex conjugate pair of eigenvalues two */
/* consecutive elements of S are set to the same value. Thus */
/* S(j), DIF(j), and the j-th columns of VL and VR all */
/* correspond to the same eigenpair (but not in general the */
/* j-th eigenpair, unless all eigenpairs are selected). */
/* If JOB = 'V', S is not referenced. */
/* DIF (output) DOUBLE PRECISION array, dimension (MM) */
/* If JOB = 'V' or 'B', the estimated reciprocal condition */
/* numbers of the selected eigenvectors, stored in consecutive */
/* elements of the array. For a complex eigenvector two */
/* consecutive elements of DIF are set to the same value. If */
/* the eigenvalues cannot be reordered to compute DIF(j), DIF(j) */
/* is set to 0; this can only occur when the true value would be */
/* very small anyway. */
/* If JOB = 'E', DIF is not referenced. */
/* MM (input) INTEGER */
/* The number of elements in the arrays S and DIF. MM >= M. */
/* M (output) INTEGER */
/* The number of elements of the arrays S and DIF used to store */
/* the specified condition numbers; for each selected real */
/* eigenvalue one element is used, and for each selected complex */
/* conjugate pair of eigenvalues, two elements are used. */
/* If HOWMNY = 'A', M is set to N. */
/* WORK (workspace/output) DOUBLE PRECISION 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 >= max(1,N). */
/* If JOB = 'V' or 'B' LWORK >= 2*N*(N+2)+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. */
/* IWORK (workspace) INTEGER array, dimension (N + 6) */
/* If JOB = 'E', IWORK is not referenced. */
/* INFO (output) INTEGER */
/* =0: Successful exit */
/* <0: If INFO = -i, the i-th argument had an illegal value */
/* Further Details */
/* =============== */
/* The reciprocal of the condition number of a generalized eigenvalue */
/* w = (a, b) is defined as */
/* S(w) = (|u'Av|**2 + |u'Bv|**2)**(1/2) / (norm(u)*norm(v)) */
/* where u and v are the left and right eigenvectors of (A, B) */
/* corresponding to w; |z| denotes the absolute value of the complex */
/* number, and norm(u) denotes the 2-norm of the vector u. */
/* The pair (a, b) corresponds to an eigenvalue w = a/b (= u'Av/u'Bv) */
/* of the matrix pair (A, B). If both a and b equal zero, then (A B) is */
/* singular and S(I) = -1 is returned. */
/* An approximate error bound on the chordal distance between the i-th */
/* computed generalized eigenvalue w and the corresponding exact */
/* eigenvalue lambda is */
/* chord(w, lambda) <= EPS * norm(A, B) / S(I) */
/* where EPS is the machine precision. */
/* The reciprocal of the condition number DIF(i) of right eigenvector u */
/* and left eigenvector v corresponding to the generalized eigenvalue w */
/* is defined as follows: */
/* a) If the i-th eigenvalue w = (a,b) is real */
/* Suppose U and V are orthogonal transformations such that */
/* U'*(A, B)*V = (S, T) = ( a * ) ( b * ) 1 */
/* ( 0 S22 ),( 0 T22 ) n-1 */
/* 1 n-1 1 n-1 */
/* Then the reciprocal condition number DIF(i) is */
/* Difl((a, b), (S22, T22)) = sigma-min( Zl ), */
/* where sigma-min(Zl) denotes the smallest singular value of the */
/* 2(n-1)-by-2(n-1) matrix */
/* Zl = [ kron(a, In-1) -kron(1, S22) ] */
/* [ kron(b, In-1) -kron(1, T22) ] . */
/* Here In-1 is the identity matrix of size n-1. kron(X, Y) is the */
/* Kronecker product between the matrices X and Y. */
/* Note that if the default method for computing DIF(i) is wanted */
/* (see DLATDF), then the parameter DIFDRI (see below) should be */
/* changed from 3 to 4 (routine DLATDF(IJOB = 2 will be used)). */
/* See DTGSYL for more details. */
/* b) If the i-th and (i+1)-th eigenvalues are complex conjugate pair, */
/* Suppose U and V are orthogonal transformations such that */
/* U'*(A, B)*V = (S, T) = ( S11 * ) ( T11 * ) 2 */
/* ( 0 S22 ),( 0 T22) n-2 */
/* 2 n-2 2 n-2 */
/* and (S11, T11) corresponds to the complex conjugate eigenvalue */
/* pair (w, conjg(w)). There exist unitary matrices U1 and V1 such */
/* that */
/* U1'*S11*V1 = ( s11 s12 ) and U1'*T11*V1 = ( t11 t12 ) */
/* ( 0 s22 ) ( 0 t22 ) */
/* where the generalized eigenvalues w = s11/t11 and */
/* conjg(w) = s22/t22. */
/* Then the reciprocal condition number DIF(i) is bounded by */
/* min( d1, max( 1, |real(s11)/real(s22)| )*d2 ) */
/* where, d1 = Difl((s11, t11), (s22, t22)) = sigma-min(Z1), where */
/* Z1 is the complex 2-by-2 matrix */
/* Z1 = [ s11 -s22 ] */
/* [ t11 -t22 ], */
/* This is done by computing (using real arithmetic) the */
/* roots of the characteristical polynomial det(Z1' * Z1 - lambda I), */
/* where Z1' denotes the conjugate transpose of Z1 and det(X) denotes */
/* the determinant of X. */
/* and d2 is an upper bound on Difl((S11, T11), (S22, T22)), i.e. an */
/* upper bound on sigma-min(Z2), where Z2 is (2n-2)-by-(2n-2) */
/* Z2 = [ kron(S11', In-2) -kron(I2, S22) ] */
/* [ kron(T11', In-2) -kron(I2, T22) ] */
/* Note that if the default method for computing DIF is wanted (see */
/* DLATDF), then the parameter DIFDRI (see below) should be changed */
/* from 3 to 4 (routine DLATDF(IJOB = 2 will be used)). See DTGSYL */
/* for more details. */
/* For each eigenvalue/vector specified by SELECT, DIF stores a */
/* Frobenius norm-based estimate of Difl. */
/* An approximate error bound for the i-th computed eigenvector VL(i) or */
/* VR(i) is given by */
/* EPS * norm(A, B) / DIF(i). */
/* See ref. [2-3] for more details and further references. */
/* Based on contributions by */
/* Bo Kagstrom and Peter Poromaa, Department of Computing Science, */
/* Umea University, S-901 87 Umea, Sweden. */
/* References */
/* ========== */
/* [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. */
/* [2] B. Kagstrom and P. Poromaa; Computing Eigenspaces with Specified */
/* Eigenvalues of a Regular Matrix Pair (A, B) and Condition */
/* Estimation: Theory, Algorithms and Software, */
/* Report UMINF - 94.04, Department of Computing Science, Umea */
/* University, S-901 87 Umea, Sweden, 1994. Also as LAPACK Working */
/* Note 87. To appear in Numerical Algorithms, 1996. */
/* [3] B. Kagstrom and P. Poromaa, LAPACK-Style Algorithms and Software */
/* for Solving the Generalized Sylvester Equation and Estimating the */
/* Separation between Regular Matrix Pairs, Report UMINF - 93.23, */
/* Department of Computing Science, Umea University, S-901 87 Umea, */
/* Sweden, December 1993, Revised April 1994, Also as LAPACK Working */
/* Note 75. To appear in ACM Trans. on Math. Software, Vol 22, */
/* No 1, 1996. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. Local Arrays .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Decode and test the input parameters */
/* Parameter adjustments */
--select;
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
b_dim1 = *ldb;
b_offset = 1 + b_dim1;
b -= b_offset;
vl_dim1 = *ldvl;
vl_offset = 1 + vl_dim1;
vl -= vl_offset;
vr_dim1 = *ldvr;
vr_offset = 1 + vr_dim1;
vr -= vr_offset;
--s;
--dif;
--work;
--iwork;
/* Function Body */
wantbh = lsame_(job, "B");
wants = lsame_(job, "E") || wantbh;
wantdf = lsame_(job, "V") || wantbh;
somcon = lsame_(howmny, "S");
*info = 0;
lquery = *lwork == -1;
if (! wants && ! wantdf) {
*info = -1;
} else if (! lsame_(howmny, "A") && ! somcon) {
*info = -2;
} else if (*n < 0) {
*info = -4;
} else if (*lda < max(1,*n)) {
*info = -6;
} else if (*ldb < max(1,*n)) {
*info = -8;
} else if (wants && *ldvl < *n) {
*info = -10;
} else if (wants && *ldvr < *n) {
*info = -12;
} else {
/* Set M to the number of eigenpairs for which condition numbers */
/* are required, and test MM. */
if (somcon) {
*m = 0;
pair = FALSE_;
i__1 = *n;
for (k = 1; k <= i__1; ++k) {
if (pair) {
pair = FALSE_;
} else {
if (k < *n) {
if (a[k + 1 + k * a_dim1] == 0.) {
if (select[k]) {
++(*m);
}
} else {
pair = TRUE_;
if (select[k] || select[k + 1]) {
*m += 2;
}
}
} else {
if (select[*n]) {
++(*m);
}
}
}
/* L10: */
}
} else {
*m = *n;
}
if (*n == 0) {
lwmin = 1;
} else if (lsame_(job, "V") || lsame_(job,
"B")) {
lwmin = (*n << 1) * (*n + 2) + 16;
} else {
lwmin = *n;
}
work[1] = (doublereal) lwmin;
if (*mm < *m) {
*info = -15;
} else if (*lwork < lwmin && ! lquery) {
*info = -18;
}
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("DTGSNA", &i__1);
return 0;
} else if (lquery) {
return 0;
}
/* Quick return if possible */
if (*n == 0) {
return 0;
}
/* Get machine constants */
eps = dlamch_("P");
smlnum = dlamch_("S") / eps;
ks = 0;
pair = FALSE_;
i__1 = *n;
for (k = 1; k <= i__1; ++k) {
/* Determine whether A(k,k) begins a 1-by-1 or 2-by-2 block. */
if (pair) {
pair = FALSE_;
goto L20;
} else {
if (k < *n) {
pair = a[k + 1 + k * a_dim1] != 0.;
}
}
/* Determine whether condition numbers are required for the k-th */
/* eigenpair. */
if (somcon) {
if (pair) {
if (! select[k] && ! select[k + 1]) {
goto L20;
}
} else {
if (! select[k]) {
goto L20;
}
}
}
++ks;
if (wants) {
/* Compute the reciprocal condition number of the k-th */
/* eigenvalue. */
if (pair) {
/* Complex eigenvalue pair. */
d__1 = dnrm2_(n, &vr[ks * vr_dim1 + 1], &c__1);
d__2 = dnrm2_(n, &vr[(ks + 1) * vr_dim1 + 1], &c__1);
rnrm = dlapy2_(&d__1, &d__2);
d__1 = dnrm2_(n, &vl[ks * vl_dim1 + 1], &c__1);
d__2 = dnrm2_(n, &vl[(ks + 1) * vl_dim1 + 1], &c__1);
lnrm = dlapy2_(&d__1, &d__2);
dgemv_("N", n, n, &c_b19, &a[a_offset], lda, &vr[ks * vr_dim1
+ 1], &c__1, &c_b21, &work[1], &c__1);
tmprr = ddot_(n, &work[1], &c__1, &vl[ks * vl_dim1 + 1], &
c__1);
tmpri = ddot_(n, &work[1], &c__1, &vl[(ks + 1) * vl_dim1 + 1],
&c__1);
dgemv_("N", n, n, &c_b19, &a[a_offset], lda, &vr[(ks + 1) *
vr_dim1 + 1], &c__1, &c_b21, &work[1], &c__1);
tmpii = ddot_(n, &work[1], &c__1, &vl[(ks + 1) * vl_dim1 + 1],
&c__1);
tmpir = ddot_(n, &work[1], &c__1, &vl[ks * vl_dim1 + 1], &
c__1);
uhav = tmprr + tmpii;
uhavi = tmpir - tmpri;
dgemv_("N", n, n, &c_b19, &b[b_offset], ldb, &vr[ks * vr_dim1
+ 1], &c__1, &c_b21, &work[1], &c__1);
tmprr = ddot_(n, &work[1], &c__1, &vl[ks * vl_dim1 + 1], &
c__1);
tmpri = ddot_(n, &work[1], &c__1, &vl[(ks + 1) * vl_dim1 + 1],
&c__1);
dgemv_("N", n, n, &c_b19, &b[b_offset], ldb, &vr[(ks + 1) *
vr_dim1 + 1], &c__1, &c_b21, &work[1], &c__1);
tmpii = ddot_(n, &work[1], &c__1, &vl[(ks + 1) * vl_dim1 + 1],
&c__1);
tmpir = ddot_(n, &work[1], &c__1, &vl[ks * vl_dim1 + 1], &
c__1);
uhbv = tmprr + tmpii;
uhbvi = tmpir - tmpri;
uhav = dlapy2_(&uhav, &uhavi);
uhbv = dlapy2_(&uhbv, &uhbvi);
cond = dlapy2_(&uhav, &uhbv);
s[ks] = cond / (rnrm * lnrm);
s[ks + 1] = s[ks];
} else {
/* Real eigenvalue. */
rnrm = dnrm2_(n, &vr[ks * vr_dim1 + 1], &c__1);
lnrm = dnrm2_(n, &vl[ks * vl_dim1 + 1], &c__1);
dgemv_("N", n, n, &c_b19, &a[a_offset], lda, &vr[ks * vr_dim1
+ 1], &c__1, &c_b21, &work[1], &c__1);
uhav = ddot_(n, &work[1], &c__1, &vl[ks * vl_dim1 + 1], &c__1)
;
dgemv_("N", n, n, &c_b19, &b[b_offset], ldb, &vr[ks * vr_dim1
+ 1], &c__1, &c_b21, &work[1], &c__1);
uhbv = ddot_(n, &work[1], &c__1, &vl[ks * vl_dim1 + 1], &c__1)
;
cond = dlapy2_(&uhav, &uhbv);
if (cond == 0.) {
s[ks] = -1.;
} else {
s[ks] = cond / (rnrm * lnrm);
}
}
}
if (wantdf) {
if (*n == 1) {
dif[ks] = dlapy2_(&a[a_dim1 + 1], &b[b_dim1 + 1]);
goto L20;
}
/* Estimate the reciprocal condition number of the k-th */
/* eigenvectors. */
if (pair) {
/* Copy the 2-by 2 pencil beginning at (A(k,k), B(k, k)). */
/* Compute the eigenvalue(s) at position K. */
work[1] = a[k + k * a_dim1];
work[2] = a[k + 1 + k * a_dim1];
work[3] = a[k + (k + 1) * a_dim1];
work[4] = a[k + 1 + (k + 1) * a_dim1];
work[5] = b[k + k * b_dim1];
work[6] = b[k + 1 + k * b_dim1];
work[7] = b[k + (k + 1) * b_dim1];
work[8] = b[k + 1 + (k + 1) * b_dim1];
d__1 = smlnum * eps;
dlag2_(&work[1], &c__2, &work[5], &c__2, &d__1, &beta, dummy1,
&alphar, dummy, &alphai);
alprqt = 1.;
c1 = (alphar * alphar + alphai * alphai + beta * beta) * 2.;
c2 = beta * 4. * beta * alphai * alphai;
root1 = c1 + sqrt(c1 * c1 - c2 * 4.);
root2 = c2 / root1;
root1 /= 2.;
/* Computing MIN */
d__1 = sqrt(root1), d__2 = sqrt(root2);
cond = min(d__1,d__2);
}
/* Copy the matrix (A, B) to the array WORK and swap the */
/* diagonal block beginning at A(k,k) to the (1,1) position. */
dlacpy_("Full", n, n, &a[a_offset], lda, &work[1], n);
dlacpy_("Full", n, n, &b[b_offset], ldb, &work[*n * *n + 1], n);
ifst = k;
ilst = 1;
i__2 = *lwork - (*n << 1) * *n;
dtgexc_(&c_false, &c_false, n, &work[1], n, &work[*n * *n + 1], n,
dummy, &c__1, dummy1, &c__1, &ifst, &ilst, &work[(*n * *
n << 1) + 1], &i__2, &ierr);
if (ierr > 0) {
/* Ill-conditioned problem - swap rejected. */
dif[ks] = 0.;
} else {
/* Reordering successful, solve generalized Sylvester */
/* equation for R and L, */
/* A22 * R - L * A11 = A12 */
/* B22 * R - L * B11 = B12, */
/* and compute estimate of Difl((A11,B11), (A22, B22)). */
n1 = 1;
if (work[2] != 0.) {
n1 = 2;
}
n2 = *n - n1;
if (n2 == 0) {
dif[ks] = cond;
} else {
i__ = *n * *n + 1;
iz = (*n << 1) * *n + 1;
i__2 = *lwork - (*n << 1) * *n;
dtgsyl_("N", &c__3, &n2, &n1, &work[*n * n1 + n1 + 1], n,
&work[1], n, &work[n1 + 1], n, &work[*n * n1 + n1
+ i__], n, &work[i__], n, &work[n1 + i__], n, &
scale, &dif[ks], &work[iz + 1], &i__2, &iwork[1],
&ierr);
if (pair) {
/* Computing MIN */
d__1 = max(1.,alprqt) * dif[ks];
dif[ks] = min(d__1,cond);
}
}
}
if (pair) {
dif[ks + 1] = dif[ks];
}
}
if (pair) {
++ks;
}
L20:
;
}
work[1] = (doublereal) lwmin;
return 0;
/* End of DTGSNA */
} /* dtgsna_ */