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/* sggbak.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"
/* Subroutine */ int sggbak_(char *job, char *side, integer *n, integer *ilo,
integer *ihi, real *lscale, real *rscale, integer *m, real *v,
integer *ldv, integer *info)
{
/* System generated locals */
integer v_dim1, v_offset, i__1;
/* Local variables */
integer i__, k;
extern logical lsame_(char *, char *);
extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *);
logical leftv;
extern /* Subroutine */ int sswap_(integer *, real *, integer *, real *,
integer *), xerbla_(char *, integer *);
logical rightv;
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SGGBAK forms the right or left eigenvectors of a real generalized */
/* eigenvalue problem A*x = lambda*B*x, by backward transformation on */
/* the computed eigenvectors of the balanced pair of matrices output by */
/* SGGBAL. */
/* Arguments */
/* ========= */
/* JOB (input) CHARACTER*1 */
/* Specifies the type of backward transformation required: */
/* = 'N': do nothing, return immediately; */
/* = 'P': do backward transformation for permutation only; */
/* = 'S': do backward transformation for scaling only; */
/* = 'B': do backward transformations for both permutation and */
/* scaling. */
/* JOB must be the same as the argument JOB supplied to SGGBAL. */
/* SIDE (input) CHARACTER*1 */
/* = 'R': V contains right eigenvectors; */
/* = 'L': V contains left eigenvectors. */
/* N (input) INTEGER */
/* The number of rows of the matrix V. N >= 0. */
/* ILO (input) INTEGER */
/* IHI (input) INTEGER */
/* The integers ILO and IHI determined by SGGBAL. */
/* 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0. */
/* LSCALE (input) REAL array, dimension (N) */
/* Details of the permutations and/or scaling factors applied */
/* to the left side of A and B, as returned by SGGBAL. */
/* RSCALE (input) REAL array, dimension (N) */
/* Details of the permutations and/or scaling factors applied */
/* to the right side of A and B, as returned by SGGBAL. */
/* M (input) INTEGER */
/* The number of columns of the matrix V. M >= 0. */
/* V (input/output) REAL array, dimension (LDV,M) */
/* On entry, the matrix of right or left eigenvectors to be */
/* transformed, as returned by STGEVC. */
/* On exit, V is overwritten by the transformed eigenvectors. */
/* LDV (input) INTEGER */
/* The leading dimension of the matrix V. LDV >= max(1,N). */
/* INFO (output) INTEGER */
/* = 0: successful exit. */
/* < 0: if INFO = -i, the i-th argument had an illegal value. */
/* Further Details */
/* =============== */
/* See R.C. Ward, Balancing the generalized eigenvalue problem, */
/* SIAM J. Sci. Stat. Comp. 2 (1981), 141-152. */
/* ===================================================================== */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters */
/* Parameter adjustments */
--lscale;
--rscale;
v_dim1 = *ldv;
v_offset = 1 + v_dim1;
v -= v_offset;
/* Function Body */
rightv = lsame_(side, "R");
leftv = lsame_(side, "L");
*info = 0;
if (! lsame_(job, "N") && ! lsame_(job, "P") && ! lsame_(job, "S")
&& ! lsame_(job, "B")) {
*info = -1;
} else if (! rightv && ! leftv) {
*info = -2;
} else if (*n < 0) {
*info = -3;
} else if (*ilo < 1) {
*info = -4;
} else if (*n == 0 && *ihi == 0 && *ilo != 1) {
*info = -4;
} else if (*n > 0 && (*ihi < *ilo || *ihi > max(1,*n))) {
*info = -5;
} else if (*n == 0 && *ilo == 1 && *ihi != 0) {
*info = -5;
} else if (*m < 0) {
*info = -8;
} else if (*ldv < max(1,*n)) {
*info = -10;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("SGGBAK", &i__1);
return 0;
}
/* Quick return if possible */
if (*n == 0) {
return 0;
}
if (*m == 0) {
return 0;
}
if (lsame_(job, "N")) {
return 0;
}
if (*ilo == *ihi) {
goto L30;
}
/* Backward balance */
if (lsame_(job, "S") || lsame_(job, "B")) {
/* Backward transformation on right eigenvectors */
if (rightv) {
i__1 = *ihi;
for (i__ = *ilo; i__ <= i__1; ++i__) {
sscal_(m, &rscale[i__], &v[i__ + v_dim1], ldv);
/* L10: */
}
}
/* Backward transformation on left eigenvectors */
if (leftv) {
i__1 = *ihi;
for (i__ = *ilo; i__ <= i__1; ++i__) {
sscal_(m, &lscale[i__], &v[i__ + v_dim1], ldv);
/* L20: */
}
}
}
/* Backward permutation */
L30:
if (lsame_(job, "P") || lsame_(job, "B")) {
/* Backward permutation on right eigenvectors */
if (rightv) {
if (*ilo == 1) {
goto L50;
}
for (i__ = *ilo - 1; i__ >= 1; --i__) {
k = rscale[i__];
if (k == i__) {
goto L40;
}
sswap_(m, &v[i__ + v_dim1], ldv, &v[k + v_dim1], ldv);
L40:
;
}
L50:
if (*ihi == *n) {
goto L70;
}
i__1 = *n;
for (i__ = *ihi + 1; i__ <= i__1; ++i__) {
k = rscale[i__];
if (k == i__) {
goto L60;
}
sswap_(m, &v[i__ + v_dim1], ldv, &v[k + v_dim1], ldv);
L60:
;
}
}
/* Backward permutation on left eigenvectors */
L70:
if (leftv) {
if (*ilo == 1) {
goto L90;
}
for (i__ = *ilo - 1; i__ >= 1; --i__) {
k = lscale[i__];
if (k == i__) {
goto L80;
}
sswap_(m, &v[i__ + v_dim1], ldv, &v[k + v_dim1], ldv);
L80:
;
}
L90:
if (*ihi == *n) {
goto L110;
}
i__1 = *n;
for (i__ = *ihi + 1; i__ <= i__1; ++i__) {
k = lscale[i__];
if (k == i__) {
goto L100;
}
sswap_(m, &v[i__ + v_dim1], ldv, &v[k + v_dim1], ldv);
L100:
;
}
}
}
L110:
return 0;
/* End of SGGBAK */
} /* sggbak_ */
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