/* zlatdf.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 doublecomplex c_b1 = {1.,0.};
static integer c__1 = 1;
static integer c_n1 = -1;
static doublereal c_b24 = 1.;
/* Subroutine */ int zlatdf_(integer *ijob, integer *n, doublecomplex *z__,
integer *ldz, doublecomplex *rhs, doublereal *rdsum, doublereal *
rdscal, integer *ipiv, integer *jpiv)
{
/* System generated locals */
integer z_dim1, z_offset, i__1, i__2, i__3, i__4, i__5;
doublecomplex z__1, z__2, z__3;
/* Builtin functions */
void z_div(doublecomplex *, doublecomplex *, doublecomplex *);
double z_abs(doublecomplex *);
void z_sqrt(doublecomplex *, doublecomplex *);
/* Local variables */
integer i__, j, k;
doublecomplex bm, bp, xm[2], xp[2];
integer info;
doublecomplex temp, work[8];
doublereal scale;
extern /* Subroutine */ int zscal_(integer *, doublecomplex *,
doublecomplex *, integer *);
doublecomplex pmone;
extern /* Double Complex */ VOID zdotc_(doublecomplex *, integer *,
doublecomplex *, integer *, doublecomplex *, integer *);
doublereal rtemp, sminu, rwork[2];
extern /* Subroutine */ int zcopy_(integer *, doublecomplex *, integer *,
doublecomplex *, integer *);
doublereal splus;
extern /* Subroutine */ int zaxpy_(integer *, doublecomplex *,
doublecomplex *, integer *, doublecomplex *, integer *), zgesc2_(
integer *, doublecomplex *, integer *, doublecomplex *, integer *,
integer *, doublereal *), zgecon_(char *, integer *,
doublecomplex *, integer *, doublereal *, doublereal *,
doublecomplex *, doublereal *, integer *);
extern doublereal dzasum_(integer *, doublecomplex *, integer *);
extern /* Subroutine */ int zlassq_(integer *, doublecomplex *, integer *,
doublereal *, doublereal *), zlaswp_(integer *, doublecomplex *,
integer *, integer *, integer *, integer *, integer *);
/* -- LAPACK auxiliary routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* ZLATDF computes the contribution to the reciprocal Dif-estimate */
/* by solving for x in Z * x = b, where b is chosen such that the norm */
/* of x is as large as possible. It is assumed that LU decomposition */
/* of Z has been computed by ZGETC2. On entry RHS = f holds the */
/* contribution from earlier solved sub-systems, and on return RHS = x. */
/* The factorization of Z returned by ZGETC2 has the form */
/* Z = P * L * U * Q, where P and Q are permutation matrices. L is lower */
/* triangular with unit diagonal elements and U is upper triangular. */
/* Arguments */
/* ========= */
/* IJOB (input) INTEGER */
/* IJOB = 2: First compute an approximative null-vector e */
/* of Z using ZGECON, e is normalized and solve for */
/* Zx = +-e - f with the sign giving the greater value of */
/* 2-norm(x). About 5 times as expensive as Default. */
/* IJOB .ne. 2: Local look ahead strategy where */
/* all entries of the r.h.s. b is choosen as either +1 or */
/* -1. Default. */
/* N (input) INTEGER */
/* The number of columns of the matrix Z. */
/* Z (input) DOUBLE PRECISION array, dimension (LDZ, N) */
/* On entry, the LU part of the factorization of the n-by-n */
/* matrix Z computed by ZGETC2: Z = P * L * U * Q */
/* LDZ (input) INTEGER */
/* The leading dimension of the array Z. LDA >= max(1, N). */
/* RHS (input/output) DOUBLE PRECISION array, dimension (N). */
/* On entry, RHS contains contributions from other subsystems. */
/* On exit, RHS contains the solution of the subsystem with */
/* entries according to the value of IJOB (see above). */
/* RDSUM (input/output) DOUBLE PRECISION */
/* On entry, the sum of squares of computed contributions to */
/* the Dif-estimate under computation by ZTGSYL, where the */
/* scaling factor RDSCAL (see below) has been factored out. */
/* On exit, the corresponding sum of squares updated with the */
/* contributions from the current sub-system. */
/* If TRANS = 'T' RDSUM is not touched. */
/* NOTE: RDSUM only makes sense when ZTGSY2 is called by CTGSYL. */
/* RDSCAL (input/output) DOUBLE PRECISION */
/* On entry, scaling factor used to prevent overflow in RDSUM. */
/* On exit, RDSCAL is updated w.r.t. the current contributions */
/* in RDSUM. */
/* If TRANS = 'T', RDSCAL is not touched. */
/* NOTE: RDSCAL only makes sense when ZTGSY2 is called by */
/* ZTGSYL. */
/* IPIV (input) INTEGER array, dimension (N). */
/* The pivot indices; for 1 <= i <= N, row i of the */
/* matrix has been interchanged with row IPIV(i). */
/* JPIV (input) INTEGER array, dimension (N). */
/* The pivot indices; for 1 <= j <= N, column j of the */
/* matrix has been interchanged with column JPIV(j). */
/* Further Details */
/* =============== */
/* Based on contributions by */
/* Bo Kagstrom and Peter Poromaa, Department of Computing Science, */
/* Umea University, S-901 87 Umea, Sweden. */
/* This routine is a further developed implementation of algorithm */
/* BSOLVE in [1] using complete pivoting in the LU factorization. */
/* [1] Bo Kagstrom and Lars Westin, */
/* Generalized Schur Methods with Condition Estimators for */
/* Solving the Generalized Sylvester Equation, IEEE Transactions */
/* on Automatic Control, Vol. 34, No. 7, July 1989, pp 745-751. */
/* [2] Peter Poromaa, */
/* On Efficient and Robust Estimators for the Separation */
/* between two Regular Matrix Pairs with Applications in */
/* Condition Estimation. Report UMINF-95.05, Department of */
/* Computing Science, Umea University, S-901 87 Umea, Sweden, */
/* 1995. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. Local Arrays .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Parameter adjustments */
z_dim1 = *ldz;
z_offset = 1 + z_dim1;
z__ -= z_offset;
--rhs;
--ipiv;
--jpiv;
/* Function Body */
if (*ijob != 2) {
/* Apply permutations IPIV to RHS */
i__1 = *n - 1;
zlaswp_(&c__1, &rhs[1], ldz, &c__1, &i__1, &ipiv[1], &c__1);
/* Solve for L-part choosing RHS either to +1 or -1. */
z__1.r = -1., z__1.i = -0.;
pmone.r = z__1.r, pmone.i = z__1.i;
i__1 = *n - 1;
for (j = 1; j <= i__1; ++j) {
i__2 = j;
z__1.r = rhs[i__2].r + 1., z__1.i = rhs[i__2].i + 0.;
bp.r = z__1.r, bp.i = z__1.i;
i__2 = j;
z__1.r = rhs[i__2].r - 1., z__1.i = rhs[i__2].i - 0.;
bm.r = z__1.r, bm.i = z__1.i;
splus = 1.;
/* Lockahead for L- part RHS(1:N-1) = +-1 */
/* SPLUS and SMIN computed more efficiently than in BSOLVE[1]. */
i__2 = *n - j;
zdotc_(&z__1, &i__2, &z__[j + 1 + j * z_dim1], &c__1, &z__[j + 1
+ j * z_dim1], &c__1);
splus += z__1.r;
i__2 = *n - j;
zdotc_(&z__1, &i__2, &z__[j + 1 + j * z_dim1], &c__1, &rhs[j + 1],
&c__1);
sminu = z__1.r;
i__2 = j;
splus *= rhs[i__2].r;
if (splus > sminu) {
i__2 = j;
rhs[i__2].r = bp.r, rhs[i__2].i = bp.i;
} else if (sminu > splus) {
i__2 = j;
rhs[i__2].r = bm.r, rhs[i__2].i = bm.i;
} else {
/* In this case the updating sums are equal and we can */
/* choose RHS(J) +1 or -1. The first time this happens we */
/* choose -1, thereafter +1. This is a simple way to get */
/* good estimates of matrices like Byers well-known example */
/* (see [1]). (Not done in BSOLVE.) */
i__2 = j;
i__3 = j;
z__1.r = rhs[i__3].r + pmone.r, z__1.i = rhs[i__3].i +
pmone.i;
rhs[i__2].r = z__1.r, rhs[i__2].i = z__1.i;
pmone.r = 1., pmone.i = 0.;
}
/* Compute the remaining r.h.s. */
i__2 = j;
z__1.r = -rhs[i__2].r, z__1.i = -rhs[i__2].i;
temp.r = z__1.r, temp.i = z__1.i;
i__2 = *n - j;
zaxpy_(&i__2, &temp, &z__[j + 1 + j * z_dim1], &c__1, &rhs[j + 1],
&c__1);
/* L10: */
}
/* Solve for U- part, lockahead for RHS(N) = +-1. This is not done */
/* In BSOLVE and will hopefully give us a better estimate because */
/* any ill-conditioning of the original matrix is transfered to U */
/* and not to L. U(N, N) is an approximation to sigma_min(LU). */
i__1 = *n - 1;
zcopy_(&i__1, &rhs[1], &c__1, work, &c__1);
i__1 = *n - 1;
i__2 = *n;
z__1.r = rhs[i__2].r + 1., z__1.i = rhs[i__2].i + 0.;
work[i__1].r = z__1.r, work[i__1].i = z__1.i;
i__1 = *n;
i__2 = *n;
z__1.r = rhs[i__2].r - 1., z__1.i = rhs[i__2].i - 0.;
rhs[i__1].r = z__1.r, rhs[i__1].i = z__1.i;
splus = 0.;
sminu = 0.;
for (i__ = *n; i__ >= 1; --i__) {
z_div(&z__1, &c_b1, &z__[i__ + i__ * z_dim1]);
temp.r = z__1.r, temp.i = z__1.i;
i__1 = i__ - 1;
i__2 = i__ - 1;
z__1.r = work[i__2].r * temp.r - work[i__2].i * temp.i, z__1.i =
work[i__2].r * temp.i + work[i__2].i * temp.r;
work[i__1].r = z__1.r, work[i__1].i = z__1.i;
i__1 = i__;
i__2 = i__;
z__1.r = rhs[i__2].r * temp.r - rhs[i__2].i * temp.i, z__1.i =
rhs[i__2].r * temp.i + rhs[i__2].i * temp.r;
rhs[i__1].r = z__1.r, rhs[i__1].i = z__1.i;
i__1 = *n;
for (k = i__ + 1; k <= i__1; ++k) {
i__2 = i__ - 1;
i__3 = i__ - 1;
i__4 = k - 1;
i__5 = i__ + k * z_dim1;
z__3.r = z__[i__5].r * temp.r - z__[i__5].i * temp.i, z__3.i =
z__[i__5].r * temp.i + z__[i__5].i * temp.r;
z__2.r = work[i__4].r * z__3.r - work[i__4].i * z__3.i,
z__2.i = work[i__4].r * z__3.i + work[i__4].i *
z__3.r;
z__1.r = work[i__3].r - z__2.r, z__1.i = work[i__3].i -
z__2.i;
work[i__2].r = z__1.r, work[i__2].i = z__1.i;
i__2 = i__;
i__3 = i__;
i__4 = k;
i__5 = i__ + k * z_dim1;
z__3.r = z__[i__5].r * temp.r - z__[i__5].i * temp.i, z__3.i =
z__[i__5].r * temp.i + z__[i__5].i * temp.r;
z__2.r = rhs[i__4].r * z__3.r - rhs[i__4].i * z__3.i, z__2.i =
rhs[i__4].r * z__3.i + rhs[i__4].i * z__3.r;
z__1.r = rhs[i__3].r - z__2.r, z__1.i = rhs[i__3].i - z__2.i;
rhs[i__2].r = z__1.r, rhs[i__2].i = z__1.i;
/* L20: */
}
splus += z_abs(&work[i__ - 1]);
sminu += z_abs(&rhs[i__]);
/* L30: */
}
if (splus > sminu) {
zcopy_(n, work, &c__1, &rhs[1], &c__1);
}
/* Apply the permutations JPIV to the computed solution (RHS) */
i__1 = *n - 1;
zlaswp_(&c__1, &rhs[1], ldz, &c__1, &i__1, &jpiv[1], &c_n1);
/* Compute the sum of squares */
zlassq_(n, &rhs[1], &c__1, rdscal, rdsum);
return 0;
}
/* ENTRY IJOB = 2 */
/* Compute approximate nullvector XM of Z */
zgecon_("I", n, &z__[z_offset], ldz, &c_b24, &rtemp, work, rwork, &info);
zcopy_(n, &work[*n], &c__1, xm, &c__1);
/* Compute RHS */
i__1 = *n - 1;
zlaswp_(&c__1, xm, ldz, &c__1, &i__1, &ipiv[1], &c_n1);
zdotc_(&z__3, n, xm, &c__1, xm, &c__1);
z_sqrt(&z__2, &z__3);
z_div(&z__1, &c_b1, &z__2);
temp.r = z__1.r, temp.i = z__1.i;
zscal_(n, &temp, xm, &c__1);
zcopy_(n, xm, &c__1, xp, &c__1);
zaxpy_(n, &c_b1, &rhs[1], &c__1, xp, &c__1);
z__1.r = -1., z__1.i = -0.;
zaxpy_(n, &z__1, xm, &c__1, &rhs[1], &c__1);
zgesc2_(n, &z__[z_offset], ldz, &rhs[1], &ipiv[1], &jpiv[1], &scale);
zgesc2_(n, &z__[z_offset], ldz, xp, &ipiv[1], &jpiv[1], &scale);
if (dzasum_(n, xp, &c__1) > dzasum_(n, &rhs[1], &c__1)) {
zcopy_(n, xp, &c__1, &rhs[1], &c__1);
}
/* Compute the sum of squares */
zlassq_(n, &rhs[1], &c__1, rdscal, rdsum);
return 0;
/* End of ZLATDF */
} /* zlatdf_ */
