/* dsbtrd.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 doublereal c_b9 = 0.;
static doublereal c_b10 = 1.;
static integer c__1 = 1;
/* Subroutine */ int dsbtrd_(char *vect, char *uplo, integer *n, integer *kd,
doublereal *ab, integer *ldab, doublereal *d__, doublereal *e,
doublereal *q, integer *ldq, doublereal *work, integer *info)
{
/* System generated locals */
integer ab_dim1, ab_offset, q_dim1, q_offset, i__1, i__2, i__3, i__4,
i__5;
/* Local variables */
integer i__, j, k, l, i2, j1, j2, nq, nr, kd1, ibl, iqb, kdn, jin, nrt,
kdm1, inca, jend, lend, jinc, incx, last;
doublereal temp;
extern /* Subroutine */ int drot_(integer *, doublereal *, integer *,
doublereal *, integer *, doublereal *, doublereal *);
integer j1end, j1inc, iqend;
extern logical lsame_(char *, char *);
logical initq, wantq, upper;
extern /* Subroutine */ int dlar2v_(integer *, doublereal *, doublereal *,
doublereal *, integer *, doublereal *, doublereal *, integer *);
integer iqaend;
extern /* Subroutine */ int dlaset_(char *, integer *, integer *,
doublereal *, doublereal *, doublereal *, integer *),
dlartg_(doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *), xerbla_(char *, integer *), dlargv_(
integer *, doublereal *, integer *, doublereal *, integer *,
doublereal *, integer *), dlartv_(integer *, doublereal *,
integer *, doublereal *, integer *, doublereal *, doublereal *,
integer *);
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DSBTRD reduces a real symmetric band matrix A to symmetric */
/* tridiagonal form T by an orthogonal similarity transformation: */
/* Q**T * A * Q = T. */
/* Arguments */
/* ========= */
/* VECT (input) CHARACTER*1 */
/* = 'N': do not form Q; */
/* = 'V': form Q; */
/* = 'U': update a matrix X, by forming X*Q. */
/* UPLO (input) CHARACTER*1 */
/* = 'U': Upper triangle of A is stored; */
/* = 'L': Lower triangle of A is stored. */
/* N (input) INTEGER */
/* The order of the matrix A. N >= 0. */
/* KD (input) INTEGER */
/* The number of superdiagonals of the matrix A if UPLO = 'U', */
/* or the number of subdiagonals if UPLO = 'L'. KD >= 0. */
/* AB (input/output) DOUBLE PRECISION array, dimension (LDAB,N) */
/* On entry, the upper or lower triangle of the symmetric band */
/* matrix A, stored in the first KD+1 rows of the array. The */
/* j-th column of A is stored in the j-th column of the array AB */
/* as follows: */
/* if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; */
/* if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd). */
/* On exit, the diagonal elements of AB are overwritten by the */
/* diagonal elements of the tridiagonal matrix T; if KD > 0, the */
/* elements on the first superdiagonal (if UPLO = 'U') or the */
/* first subdiagonal (if UPLO = 'L') are overwritten by the */
/* off-diagonal elements of T; the rest of AB is overwritten by */
/* values generated during the reduction. */
/* LDAB (input) INTEGER */
/* The leading dimension of the array AB. LDAB >= KD+1. */
/* D (output) DOUBLE PRECISION array, dimension (N) */
/* The diagonal elements of the tridiagonal matrix T. */
/* E (output) DOUBLE PRECISION array, dimension (N-1) */
/* The off-diagonal elements of the tridiagonal matrix T: */
/* E(i) = T(i,i+1) if UPLO = 'U'; E(i) = T(i+1,i) if UPLO = 'L'. */
/* Q (input/output) DOUBLE PRECISION array, dimension (LDQ,N) */
/* On entry, if VECT = 'U', then Q must contain an N-by-N */
/* matrix X; if VECT = 'N' or 'V', then Q need not be set. */
/* On exit: */
/* if VECT = 'V', Q contains the N-by-N orthogonal matrix Q; */
/* if VECT = 'U', Q contains the product X*Q; */
/* if VECT = 'N', the array Q is not referenced. */
/* LDQ (input) INTEGER */
/* The leading dimension of the array Q. */
/* LDQ >= 1, and LDQ >= N if VECT = 'V' or 'U'. */
/* WORK (workspace) DOUBLE PRECISION array, dimension (N) */
/* INFO (output) INTEGER */
/* = 0: successful exit */
/* < 0: if INFO = -i, the i-th argument had an illegal value */
/* Further Details */
/* =============== */
/* Modified by Linda Kaufman, Bell Labs. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters */
/* Parameter adjustments */
ab_dim1 = *ldab;
ab_offset = 1 + ab_dim1;
ab -= ab_offset;
--d__;
--e;
q_dim1 = *ldq;
q_offset = 1 + q_dim1;
q -= q_offset;
--work;
/* Function Body */
initq = lsame_(vect, "V");
wantq = initq || lsame_(vect, "U");
upper = lsame_(uplo, "U");
kd1 = *kd + 1;
kdm1 = *kd - 1;
incx = *ldab - 1;
iqend = 1;
*info = 0;
if (! wantq && ! lsame_(vect, "N")) {
*info = -1;
} else if (! upper && ! lsame_(uplo, "L")) {
*info = -2;
} else if (*n < 0) {
*info = -3;
} else if (*kd < 0) {
*info = -4;
} else if (*ldab < kd1) {
*info = -6;
} else if (*ldq < max(1,*n) && wantq) {
*info = -10;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("DSBTRD", &i__1);
return 0;
}
/* Quick return if possible */
if (*n == 0) {
return 0;
}
/* Initialize Q to the unit matrix, if needed */
if (initq) {
dlaset_("Full", n, n, &c_b9, &c_b10, &q[q_offset], ldq);
}
/* Wherever possible, plane rotations are generated and applied in */
/* vector operations of length NR over the index set J1:J2:KD1. */
/* The cosines and sines of the plane rotations are stored in the */
/* arrays D and WORK. */
inca = kd1 * *ldab;
/* Computing MIN */
i__1 = *n - 1;
kdn = min(i__1,*kd);
if (upper) {
if (*kd > 1) {
/* Reduce to tridiagonal form, working with upper triangle */
nr = 0;
j1 = kdn + 2;
j2 = 1;
i__1 = *n - 2;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Reduce i-th row of matrix to tridiagonal form */
for (k = kdn + 1; k >= 2; --k) {
j1 += kdn;
j2 += kdn;
if (nr > 0) {
/* generate plane rotations to annihilate nonzero */
/* elements which have been created outside the band */
dlargv_(&nr, &ab[(j1 - 1) * ab_dim1 + 1], &inca, &
work[j1], &kd1, &d__[j1], &kd1);
/* apply rotations from the right */
/* Dependent on the the number of diagonals either */
/* DLARTV or DROT is used */
if (nr >= (*kd << 1) - 1) {
i__2 = *kd - 1;
for (l = 1; l <= i__2; ++l) {
dlartv_(&nr, &ab[l + 1 + (j1 - 1) * ab_dim1],
&inca, &ab[l + j1 * ab_dim1], &inca, &
d__[j1], &work[j1], &kd1);
/* L10: */
}
} else {
jend = j1 + (nr - 1) * kd1;
i__2 = jend;
i__3 = kd1;
for (jinc = j1; i__3 < 0 ? jinc >= i__2 : jinc <=
i__2; jinc += i__3) {
drot_(&kdm1, &ab[(jinc - 1) * ab_dim1 + 2], &
c__1, &ab[jinc * ab_dim1 + 1], &c__1,
&d__[jinc], &work[jinc]);
/* L20: */
}
}
}
if (k > 2) {
if (k <= *n - i__ + 1) {
/* generate plane rotation to annihilate a(i,i+k-1) */
/* within the band */
dlartg_(&ab[*kd - k + 3 + (i__ + k - 2) * ab_dim1]
, &ab[*kd - k + 2 + (i__ + k - 1) *
ab_dim1], &d__[i__ + k - 1], &work[i__ +
k - 1], &temp);
ab[*kd - k + 3 + (i__ + k - 2) * ab_dim1] = temp;
/* apply rotation from the right */
i__3 = k - 3;
drot_(&i__3, &ab[*kd - k + 4 + (i__ + k - 2) *
ab_dim1], &c__1, &ab[*kd - k + 3 + (i__ +
k - 1) * ab_dim1], &c__1, &d__[i__ + k -
1], &work[i__ + k - 1]);
}
++nr;
j1 = j1 - kdn - 1;
}
/* apply plane rotations from both sides to diagonal */
/* blocks */
if (nr > 0) {
dlar2v_(&nr, &ab[kd1 + (j1 - 1) * ab_dim1], &ab[kd1 +
j1 * ab_dim1], &ab[*kd + j1 * ab_dim1], &inca,
&d__[j1], &work[j1], &kd1);
}
/* apply plane rotations from the left */
if (nr > 0) {
if ((*kd << 1) - 1 < nr) {
/* Dependent on the the number of diagonals either */
/* DLARTV or DROT is used */
i__3 = *kd - 1;
for (l = 1; l <= i__3; ++l) {
if (j2 + l > *n) {
nrt = nr - 1;
} else {
nrt = nr;
}
if (nrt > 0) {
dlartv_(&nrt, &ab[*kd - l + (j1 + l) *
ab_dim1], &inca, &ab[*kd - l + 1
+ (j1 + l) * ab_dim1], &inca, &
d__[j1], &work[j1], &kd1);
}
/* L30: */
}
} else {
j1end = j1 + kd1 * (nr - 2);
if (j1end >= j1) {
i__3 = j1end;
i__2 = kd1;
for (jin = j1; i__2 < 0 ? jin >= i__3 : jin <=
i__3; jin += i__2) {
i__4 = *kd - 1;
drot_(&i__4, &ab[*kd - 1 + (jin + 1) *
ab_dim1], &incx, &ab[*kd + (jin +
1) * ab_dim1], &incx, &d__[jin], &
work[jin]);
/* L40: */
}
}
/* Computing MIN */
i__2 = kdm1, i__3 = *n - j2;
lend = min(i__2,i__3);
last = j1end + kd1;
if (lend > 0) {
drot_(&lend, &ab[*kd - 1 + (last + 1) *
ab_dim1], &incx, &ab[*kd + (last + 1)
* ab_dim1], &incx, &d__[last], &work[
last]);
}
}
}
if (wantq) {
/* accumulate product of plane rotations in Q */
if (initq) {
/* take advantage of the fact that Q was */
/* initially the Identity matrix */
iqend = max(iqend,j2);
/* Computing MAX */
i__2 = 0, i__3 = k - 3;
i2 = max(i__2,i__3);
iqaend = i__ * *kd + 1;
if (k == 2) {
iqaend += *kd;
}
iqaend = min(iqaend,iqend);
i__2 = j2;
i__3 = kd1;
for (j = j1; i__3 < 0 ? j >= i__2 : j <= i__2; j
+= i__3) {
ibl = i__ - i2 / kdm1;
++i2;
/* Computing MAX */
i__4 = 1, i__5 = j - ibl;
iqb = max(i__4,i__5);
nq = iqaend + 1 - iqb;
/* Computing MIN */
i__4 = iqaend + *kd;
iqaend = min(i__4,iqend);
drot_(&nq, &q[iqb + (j - 1) * q_dim1], &c__1,
&q[iqb + j * q_dim1], &c__1, &d__[j],
&work[j]);
/* L50: */
}
} else {
i__3 = j2;
i__2 = kd1;
for (j = j1; i__2 < 0 ? j >= i__3 : j <= i__3; j
+= i__2) {
drot_(n, &q[(j - 1) * q_dim1 + 1], &c__1, &q[
j * q_dim1 + 1], &c__1, &d__[j], &
work[j]);
/* L60: */
}
}
}
if (j2 + kdn > *n) {
/* adjust J2 to keep within the bounds of the matrix */
--nr;
j2 = j2 - kdn - 1;
}
i__2 = j2;
i__3 = kd1;
for (j = j1; i__3 < 0 ? j >= i__2 : j <= i__2; j += i__3)
{
/* create nonzero element a(j-1,j+kd) outside the band */
/* and store it in WORK */
work[j + *kd] = work[j] * ab[(j + *kd) * ab_dim1 + 1];
ab[(j + *kd) * ab_dim1 + 1] = d__[j] * ab[(j + *kd) *
ab_dim1 + 1];
/* L70: */
}
/* L80: */
}
/* L90: */
}
}
if (*kd > 0) {
/* copy off-diagonal elements to E */
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
e[i__] = ab[*kd + (i__ + 1) * ab_dim1];
/* L100: */
}
} else {
/* set E to zero if original matrix was diagonal */
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
e[i__] = 0.;
/* L110: */
}
}
/* copy diagonal elements to D */
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
d__[i__] = ab[kd1 + i__ * ab_dim1];
/* L120: */
}
} else {
if (*kd > 1) {
/* Reduce to tridiagonal form, working with lower triangle */
nr = 0;
j1 = kdn + 2;
j2 = 1;
i__1 = *n - 2;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Reduce i-th column of matrix to tridiagonal form */
for (k = kdn + 1; k >= 2; --k) {
j1 += kdn;
j2 += kdn;
if (nr > 0) {
/* generate plane rotations to annihilate nonzero */
/* elements which have been created outside the band */
dlargv_(&nr, &ab[kd1 + (j1 - kd1) * ab_dim1], &inca, &
work[j1], &kd1, &d__[j1], &kd1);
/* apply plane rotations from one side */
/* Dependent on the the number of diagonals either */
/* DLARTV or DROT is used */
if (nr > (*kd << 1) - 1) {
i__3 = *kd - 1;
for (l = 1; l <= i__3; ++l) {
dlartv_(&nr, &ab[kd1 - l + (j1 - kd1 + l) *
ab_dim1], &inca, &ab[kd1 - l + 1 + (
j1 - kd1 + l) * ab_dim1], &inca, &d__[
j1], &work[j1], &kd1);
/* L130: */
}
} else {
jend = j1 + kd1 * (nr - 1);
i__3 = jend;
i__2 = kd1;
for (jinc = j1; i__2 < 0 ? jinc >= i__3 : jinc <=
i__3; jinc += i__2) {
drot_(&kdm1, &ab[*kd + (jinc - *kd) * ab_dim1]
, &incx, &ab[kd1 + (jinc - *kd) *
ab_dim1], &incx, &d__[jinc], &work[
jinc]);
/* L140: */
}
}
}
if (k > 2) {
if (k <= *n - i__ + 1) {
/* generate plane rotation to annihilate a(i+k-1,i) */
/* within the band */
dlartg_(&ab[k - 1 + i__ * ab_dim1], &ab[k + i__ *
ab_dim1], &d__[i__ + k - 1], &work[i__ +
k - 1], &temp);
ab[k - 1 + i__ * ab_dim1] = temp;
/* apply rotation from the left */
i__2 = k - 3;
i__3 = *ldab - 1;
i__4 = *ldab - 1;
drot_(&i__2, &ab[k - 2 + (i__ + 1) * ab_dim1], &
i__3, &ab[k - 1 + (i__ + 1) * ab_dim1], &
i__4, &d__[i__ + k - 1], &work[i__ + k -
1]);
}
++nr;
j1 = j1 - kdn - 1;
}
/* apply plane rotations from both sides to diagonal */
/* blocks */
if (nr > 0) {
dlar2v_(&nr, &ab[(j1 - 1) * ab_dim1 + 1], &ab[j1 *
ab_dim1 + 1], &ab[(j1 - 1) * ab_dim1 + 2], &
inca, &d__[j1], &work[j1], &kd1);
}
/* apply plane rotations from the right */
/* Dependent on the the number of diagonals either */
/* DLARTV or DROT is used */
if (nr > 0) {
if (nr > (*kd << 1) - 1) {
i__2 = *kd - 1;
for (l = 1; l <= i__2; ++l) {
if (j2 + l > *n) {
nrt = nr - 1;
} else {
nrt = nr;
}
if (nrt > 0) {
dlartv_(&nrt, &ab[l + 2 + (j1 - 1) *
ab_dim1], &inca, &ab[l + 1 + j1 *
ab_dim1], &inca, &d__[j1], &work[
j1], &kd1);
}
/* L150: */
}
} else {
j1end = j1 + kd1 * (nr - 2);
if (j1end >= j1) {
i__2 = j1end;
i__3 = kd1;
for (j1inc = j1; i__3 < 0 ? j1inc >= i__2 :
j1inc <= i__2; j1inc += i__3) {
drot_(&kdm1, &ab[(j1inc - 1) * ab_dim1 +
3], &c__1, &ab[j1inc * ab_dim1 +
2], &c__1, &d__[j1inc], &work[
j1inc]);
/* L160: */
}
}
/* Computing MIN */
i__3 = kdm1, i__2 = *n - j2;
lend = min(i__3,i__2);
last = j1end + kd1;
if (lend > 0) {
drot_(&lend, &ab[(last - 1) * ab_dim1 + 3], &
c__1, &ab[last * ab_dim1 + 2], &c__1,
&d__[last], &work[last]);
}
}
}
if (wantq) {
/* accumulate product of plane rotations in Q */
if (initq) {
/* take advantage of the fact that Q was */
/* initially the Identity matrix */
iqend = max(iqend,j2);
/* Computing MAX */
i__3 = 0, i__2 = k - 3;
i2 = max(i__3,i__2);
iqaend = i__ * *kd + 1;
if (k == 2) {
iqaend += *kd;
}
iqaend = min(iqaend,iqend);
i__3 = j2;
i__2 = kd1;
for (j = j1; i__2 < 0 ? j >= i__3 : j <= i__3; j
+= i__2) {
ibl = i__ - i2 / kdm1;
++i2;
/* Computing MAX */
i__4 = 1, i__5 = j - ibl;
iqb = max(i__4,i__5);
nq = iqaend + 1 - iqb;
/* Computing MIN */
i__4 = iqaend + *kd;
iqaend = min(i__4,iqend);
drot_(&nq, &q[iqb + (j - 1) * q_dim1], &c__1,
&q[iqb + j * q_dim1], &c__1, &d__[j],
&work[j]);
/* L170: */
}
} else {
i__2 = j2;
i__3 = kd1;
for (j = j1; i__3 < 0 ? j >= i__2 : j <= i__2; j
+= i__3) {
drot_(n, &q[(j - 1) * q_dim1 + 1], &c__1, &q[
j * q_dim1 + 1], &c__1, &d__[j], &
work[j]);
/* L180: */
}
}
}
if (j2 + kdn > *n) {
/* adjust J2 to keep within the bounds of the matrix */
--nr;
j2 = j2 - kdn - 1;
}
i__3 = j2;
i__2 = kd1;
for (j = j1; i__2 < 0 ? j >= i__3 : j <= i__3; j += i__2)
{
/* create nonzero element a(j+kd,j-1) outside the */
/* band and store it in WORK */
work[j + *kd] = work[j] * ab[kd1 + j * ab_dim1];
ab[kd1 + j * ab_dim1] = d__[j] * ab[kd1 + j * ab_dim1]
;
/* L190: */
}
/* L200: */
}
/* L210: */
}
}
if (*kd > 0) {
/* copy off-diagonal elements to E */
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
e[i__] = ab[i__ * ab_dim1 + 2];
/* L220: */
}
} else {
/* set E to zero if original matrix was diagonal */
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
e[i__] = 0.;
/* L230: */
}
}
/* copy diagonal elements to D */
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
d__[i__] = ab[i__ * ab_dim1 + 1];
/* L240: */
}
}
return 0;
/* End of DSBTRD */
} /* dsbtrd_ */