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/* ../../../dependencies/lapack/src/ctrexc.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"
/* Table of constant values */
static integer c__1 = 1;
/* Subroutine */ int ctrexc_(char *compq, integer *n, complex *t, integer *
ldt, complex *q, integer *ldq, integer *ifst, integer *ilst, integer *
info, ftnlen compq_len)
{
/* System generated locals */
integer q_dim1, q_offset, t_dim1, t_offset, i__1, i__2, i__3;
complex q__1;
/* Builtin functions */
void r_cnjg(complex *, complex *);
/* Local variables */
static integer k, m1, m2, m3;
static real cs;
static complex t11, t22, sn, temp;
extern /* Subroutine */ int crot_(integer *, complex *, integer *,
complex *, integer *, real *, complex *);
extern logical lsame_(char *, char *, ftnlen, ftnlen);
static logical wantq;
extern /* Subroutine */ int clartg_(complex *, complex *, real *, complex
*, complex *), xerbla_(char *, integer *, ftnlen);
/* -- LAPACK routine (version 3.0) -- */
/* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/* Courant Institute, Argonne National Lab, and Rice University */
/* March 31, 1993 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* CTREXC reorders the Schur factorization of a complex matrix */
/* A = Q*T*Q**H, so that the diagonal element of T with row index IFST */
/* is moved to row ILST. */
/* The Schur form T is reordered by a unitary similarity transformation */
/* Z**H*T*Z, and optionally the matrix Q of Schur vectors is updated by */
/* postmultplying it with Z. */
/* Arguments */
/* ========= */
/* COMPQ (input) CHARACTER*1 */
/* = 'V': update the matrix Q of Schur vectors; */
/* = 'N': do not update Q. */
/* N (input) INTEGER */
/* The order of the matrix T. N >= 0. */
/* T (input/output) COMPLEX array, dimension (LDT,N) */
/* On entry, the upper triangular matrix T. */
/* On exit, the reordered upper triangular matrix. */
/* LDT (input) INTEGER */
/* The leading dimension of the array T. LDT >= max(1,N). */
/* Q (input/output) COMPLEX array, dimension (LDQ,N) */
/* On entry, if COMPQ = 'V', the matrix Q of Schur vectors. */
/* On exit, if COMPQ = 'V', Q has been postmultiplied by the */
/* unitary transformation matrix Z which reorders T. */
/* If COMPQ = 'N', Q is not referenced. */
/* LDQ (input) INTEGER */
/* The leading dimension of the array Q. LDQ >= max(1,N). */
/* IFST (input) INTEGER */
/* ILST (input) INTEGER */
/* Specify the reordering of the diagonal elements of T: */
/* The element with row index IFST is moved to row ILST by a */
/* sequence of transpositions between adjacent elements. */
/* 1 <= IFST <= N; 1 <= ILST <= N. */
/* INFO (output) INTEGER */
/* = 0: successful exit */
/* < 0: if INFO = -i, the i-th argument had an illegal value */
/* ===================================================================== */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Decode and test the input parameters. */
/* Parameter adjustments */
t_dim1 = *ldt;
t_offset = 1 + t_dim1;
t -= t_offset;
q_dim1 = *ldq;
q_offset = 1 + q_dim1;
q -= q_offset;
/* Function Body */
*info = 0;
wantq = lsame_(compq, "V", (ftnlen)1, (ftnlen)1);
if (! lsame_(compq, "N", (ftnlen)1, (ftnlen)1) && ! wantq) {
*info = -1;
} else if (*n < 0) {
*info = -2;
} else if (*ldt < max(1,*n)) {
*info = -4;
} else if (*ldq < 1 || wantq && *ldq < max(1,*n)) {
*info = -6;
} else if (*ifst < 1 || *ifst > *n) {
*info = -7;
} else if (*ilst < 1 || *ilst > *n) {
*info = -8;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("CTREXC", &i__1, (ftnlen)6);
return 0;
}
/* Quick return if possible */
if (*n == 1 || *ifst == *ilst) {
return 0;
}
if (*ifst < *ilst) {
/* Move the IFST-th diagonal element forward down the diagonal. */
m1 = 0;
m2 = -1;
m3 = 1;
} else {
/* Move the IFST-th diagonal element backward up the diagonal. */
m1 = -1;
m2 = 0;
m3 = -1;
}
i__1 = *ilst + m2;
i__2 = m3;
for (k = *ifst + m1; i__2 < 0 ? k >= i__1 : k <= i__1; k += i__2) {
/* Interchange the k-th and (k+1)-th diagonal elements. */
i__3 = k + k * t_dim1;
t11.r = t[i__3].r, t11.i = t[i__3].i;
i__3 = k + 1 + (k + 1) * t_dim1;
t22.r = t[i__3].r, t22.i = t[i__3].i;
/* Determine the transformation to perform the interchange. */
q__1.r = t22.r - t11.r, q__1.i = t22.i - t11.i;
clartg_(&t[k + (k + 1) * t_dim1], &q__1, &cs, &sn, &temp);
/* Apply transformation to the matrix T. */
if (k + 2 <= *n) {
i__3 = *n - k - 1;
crot_(&i__3, &t[k + (k + 2) * t_dim1], ldt, &t[k + 1 + (k + 2) *
t_dim1], ldt, &cs, &sn);
}
i__3 = k - 1;
r_cnjg(&q__1, &sn);
crot_(&i__3, &t[k * t_dim1 + 1], &c__1, &t[(k + 1) * t_dim1 + 1], &
c__1, &cs, &q__1);
i__3 = k + k * t_dim1;
t[i__3].r = t22.r, t[i__3].i = t22.i;
i__3 = k + 1 + (k + 1) * t_dim1;
t[i__3].r = t11.r, t[i__3].i = t11.i;
if (wantq) {
/* Accumulate transformation in the matrix Q. */
r_cnjg(&q__1, &sn);
crot_(n, &q[k * q_dim1 + 1], &c__1, &q[(k + 1) * q_dim1 + 1], &
c__1, &cs, &q__1);
}
/* L10: */
}
return 0;
/* End of CTREXC */
} /* ctrexc_ */
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