Subroutine */ int igraphdnapps_(integer *n, integer *kev, integer *np,
doublereal *shiftr, doublereal *shifti, doublereal *v, integer *ldv,
doublereal *h__, integer *ldh, doublereal *resid, doublereal *q,
integer *ldq, doublereal *workl, doublereal *workd)
{
/* Initialized data */
IGRAPH_F77_SAVE logical first = TRUE_;
/* System generated locals */
integer h_dim1, h_offset, v_dim1, v_offset, q_dim1, q_offset, i__1, i__2,
i__3, i__4;
doublereal d__1, d__2;
/* Local variables */
doublereal c__, f, g;
integer i__, j;
doublereal r__, s, t, u[3];
real t0, t1;
doublereal h11, h12, h21, h22, h32;
integer jj, ir, nr;
doublereal tau;
IGRAPH_F77_SAVE doublereal ulp;
doublereal tst1;
integer iend;
IGRAPH_F77_SAVE doublereal unfl, ovfl;
extern /* Subroutine */ int igraphdscal_(integer *, doublereal *, doublereal *,
integer *), igraphdlarf_(char *, integer *, integer *, doublereal *,
integer *, doublereal *, doublereal *, integer *, doublereal *);
logical cconj;
extern /* Subroutine */ int igraphdgemv_(char *, integer *, integer *,
doublereal *, doublereal *, integer *, doublereal *, integer *,
doublereal *, doublereal *, integer *), igraphdcopy_(integer *,
doublereal *, integer *, doublereal *, integer *), igraphdaxpy_(integer
*, doublereal *, doublereal *, integer *, doublereal *, integer *)
, igraphdmout_(integer *, integer *, integer *, doublereal *, integer *,
integer *, char *, ftnlen), igraphdvout_(integer *, integer *,
doublereal *, integer *, char *, ftnlen), igraphivout_(integer *,
integer *, integer *, integer *, char *, ftnlen);
extern doublereal igraphdlapy2_(doublereal *, doublereal *);
extern /* Subroutine */ int igraphdlabad_(doublereal *, doublereal *);
extern doublereal igraphdlamch_(char *);
extern /* Subroutine */ int igraphdlarfg_(integer *, doublereal *, doublereal *,
integer *, doublereal *);
doublereal sigmai;
extern doublereal igraphdlanhs_(char *, integer *, doublereal *, integer *,
doublereal *);
extern /* Subroutine */ int igraphsecond_(real *), igraphdlacpy_(char *, integer *,
integer *, doublereal *, integer *, doublereal *, integer *), igraphdlaset_(char *, integer *, integer *, doublereal *,
doublereal *, doublereal *, integer *), igraphdlartg_(
doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *);
integer logfil, ndigit;
doublereal sigmar;
integer mnapps = 0, msglvl;
real tnapps = 0.;
integer istart;
IGRAPH_F77_SAVE doublereal smlnum;
integer kplusp;
/* %----------------------------------------------------%
| Include files for debugging and timing information |
%----------------------------------------------------%
%------------------%
| Scalar Arguments |
%------------------%
%-----------------%
| Array Arguments |
%-----------------%
%------------%
| Parameters |
%------------%
%------------------------%
| Local Scalars & Arrays |
%------------------------%
%----------------------%
| External Subroutines |
%----------------------%
%--------------------%
| External Functions |
%--------------------%
%----------------------%
| Intrinsics Functions |
%----------------------%
%----------------%
| Data statments |
%----------------%
Parameter adjustments */
--workd;
--resid;
--workl;
--shifti;
--shiftr;
v_dim1 = *ldv;
v_offset = 1 + v_dim1;
v -= v_offset;
h_dim1 = *ldh;
h_offset = 1 + h_dim1;
h__ -= h_offset;
q_dim1 = *ldq;
q_offset = 1 + q_dim1;
q -= q_offset;
/* Function Body
%-----------------------%
| Executable Statements |
%-----------------------% */
if (first) {
/* %-----------------------------------------------%
| Set machine-dependent constants for the |
| stopping criterion. If norm(H) <= sqrt(OVFL), |
| overflow should not occur. |
| REFERENCE: LAPACK subroutine dlahqr |
%-----------------------------------------------% */
unfl = igraphdlamch_("safe minimum");
ovfl = 1. / unfl;
igraphdlabad_(&unfl, &ovfl);
ulp = igraphdlamch_("precision");
smlnum = unfl * (*n / ulp);
first = FALSE_;
}
/* %-------------------------------%
| Initialize timing statistics |
| & message level for debugging |
%-------------------------------% */
igraphsecond_(&t0);
msglvl = mnapps;
kplusp = *kev + *np;
/* %--------------------------------------------%
| Initialize Q to the identity to accumulate |
| the rotations and reflections |
%--------------------------------------------% */
igraphdlaset_("All", &kplusp, &kplusp, &c_b5, &c_b6, &q[q_offset], ldq);
/* %----------------------------------------------%
| Quick return if there are no shifts to apply |
%----------------------------------------------% */
if (*np == 0) {
goto L9000;
}
/* %----------------------------------------------%
| Chase the bulge with the application of each |
| implicit shift. Each shift is applied to the |
| whole matrix including each block. |
%----------------------------------------------% */
cconj = FALSE_;
i__1 = *np;
for (jj = 1; jj <= i__1; ++jj) {
sigmar = shiftr[jj];
sigmai = shifti[jj];
if (msglvl > 2) {
igraphivout_(&logfil, &c__1, &jj, &ndigit, "_napps: shift number.", (
ftnlen)21);
igraphdvout_(&logfil, &c__1, &sigmar, &ndigit, "_napps: The real part "
"of the shift ", (ftnlen)35);
igraphdvout_(&logfil, &c__1, &sigmai, &ndigit, "_napps: The imaginary "
"part of the shift ", (ftnlen)40);
}
/* %-------------------------------------------------%
| The following set of conditionals is necessary |
| in order that complex conjugate pairs of shifts |
| are applied together or not at all. |
%-------------------------------------------------% */
if (cconj) {
/* %-----------------------------------------%
| cconj = .true. means the previous shift |
| had non-zero imaginary part. |
%-----------------------------------------% */
cconj = FALSE_;
goto L110;
} else if (jj < *np && abs(sigmai) > 0.) {
/* %------------------------------------%
| Start of a complex conjugate pair. |
%------------------------------------% */
cconj = TRUE_;
} else if (jj == *np && abs(sigmai) > 0.) {
/* %----------------------------------------------%
| The last shift has a nonzero imaginary part. |
| Don't apply it; thus the order of the |
| compressed H is order KEV+1 since only np-1 |
| were applied. |
%----------------------------------------------% */
++(*kev);
goto L110;
}
istart = 1;
L20:
/* %--------------------------------------------------%
| if sigmai = 0 then |
| Apply the jj-th shift ... |
| else |
| Apply the jj-th and (jj+1)-th together ... |
| (Note that jj < np at this point in the code) |
| end |
| to the current block of H. The next do loop |
| determines the current block ; |
%--------------------------------------------------% */
i__2 = kplusp - 1;
for (i__ = istart; i__ <= i__2; ++i__) {
/* %----------------------------------------%
| Check for splitting and deflation. Use |
| a standard test as in the QR algorithm |
| REFERENCE: LAPACK subroutine dlahqr |
%----------------------------------------% */
tst1 = (d__1 = h__[i__ + i__ * h_dim1], abs(d__1)) + (d__2 = h__[
i__ + 1 + (i__ + 1) * h_dim1], abs(d__2));
if (tst1 == 0.) {
i__3 = kplusp - jj + 1;
tst1 = igraphdlanhs_("1", &i__3, &h__[h_offset], ldh, &workl[1]);
}
/* Computing MAX */
d__2 = ulp * tst1;
if ((d__1 = h__[i__ + 1 + i__ * h_dim1], abs(d__1)) <= max(d__2,
smlnum)) {
if (msglvl > 0) {
igraphivout_(&logfil, &c__1, &i__, &ndigit, "_napps: matrix sp"
"litting at row/column no.", (ftnlen)42);
igraphivout_(&logfil, &c__1, &jj, &ndigit, "_napps: matrix spl"
"itting with shift number.", (ftnlen)43);
igraphdvout_(&logfil, &c__1, &h__[i__ + 1 + i__ * h_dim1], &
ndigit, "_napps: off diagonal element.", (ftnlen)
29);
}
iend = i__;
h__[i__ + 1 + i__ * h_dim1] = 0.;
goto L40;
}
/* L30: */
}
iend = kplusp;
L40:
if (msglvl > 2) {
igraphivout_(&logfil, &c__1, &istart, &ndigit, "_napps: Start of curre"
"nt block ", (ftnlen)31);
igraphivout_(&logfil, &c__1, &iend, &ndigit, "_napps: End of current b"
"lock ", (ftnlen)29);
}
/* %------------------------------------------------%
| No reason to apply a shift to block of order 1 |
%------------------------------------------------% */
if (istart == iend) {
goto L100;
}
/* %------------------------------------------------------%
| If istart + 1 = iend then no reason to apply a |
| complex conjugate pair of shifts on a 2 by 2 matrix. |
%------------------------------------------------------% */
if (istart + 1 == iend && abs(sigmai) > 0.) {
goto L100;
}
h11 = h__[istart + istart * h_dim1];
h21 = h__[istart + 1 + istart * h_dim1];
if (abs(sigmai) <= 0.) {
/* %---------------------------------------------%
| Real-valued shift ==> apply single shift QR |
%---------------------------------------------% */
f = h11 - sigmar;
g = h21;
i__2 = iend - 1;
for (i__ = istart; i__ <= i__2; ++i__) {
/* %-----------------------------------------------------%
| Contruct the plane rotation G to zero out the bulge |
%-----------------------------------------------------% */
igraphdlartg_(&f, &g, &c__, &s, &r__);
if (i__ > istart) {
/* %-------------------------------------------%
| The following ensures that h(1:iend-1,1), |
| the first iend-2 off diagonal of elements |
| H, remain non negative. |
%-------------------------------------------% */
if (r__ < 0.) {
r__ = -r__;
c__ = -c__;
s = -s;
}
h__[i__ + (i__ - 1) * h_dim1] = r__;
h__[i__ + 1 + (i__ - 1) * h_dim1] = 0.;
}
/* %---------------------------------------------%
| Apply rotation to the left of H; H <- G'*H |
%---------------------------------------------% */
i__3 = kplusp;
for (j = i__; j <= i__3; ++j) {
t = c__ * h__[i__ + j * h_dim1] + s * h__[i__ + 1 + j *
h_dim1];
h__[i__ + 1 + j * h_dim1] = -s * h__[i__ + j * h_dim1] +
c__ * h__[i__ + 1 + j * h_dim1];
h__[i__ + j * h_dim1] = t;
/* L50: */
}
/* %---------------------------------------------%
| Apply rotation to the right of H; H <- H*G |
%---------------------------------------------%
Computing MIN */
i__4 = i__ + 2;
i__3 = min(i__4,iend);
for (j = 1; j <= i__3; ++j) {
t = c__ * h__[j + i__ * h_dim1] + s * h__[j + (i__ + 1) *
h_dim1];
h__[j + (i__ + 1) * h_dim1] = -s * h__[j + i__ * h_dim1]
+ c__ * h__[j + (i__ + 1) * h_dim1];
h__[j + i__ * h_dim1] = t;
/* L60: */
}
/* %----------------------------------------------------%
| Accumulate the rotation in the matrix Q; Q <- Q*G |
%----------------------------------------------------%
Computing MIN */
i__4 = j + jj;
i__3 = min(i__4,kplusp);
for (j = 1; j <= i__3; ++j) {
t = c__ * q[j + i__ * q_dim1] + s * q[j + (i__ + 1) *
q_dim1];
q[j + (i__ + 1) * q_dim1] = -s * q[j + i__ * q_dim1] +
c__ * q[j + (i__ + 1) * q_dim1];
q[j + i__ * q_dim1] = t;
/* L70: */
}
/* %---------------------------%
| Prepare for next rotation |
%---------------------------% */
if (i__ < iend - 1) {
f = h__[i__ + 1 + i__ * h_dim1];
g = h__[i__ + 2 + i__ * h_dim1];
}
/* L80: */
}
/* %-----------------------------------%
| Finished applying the real shift. |
%-----------------------------------% */
} else {
/* %----------------------------------------------------%
| Complex conjugate shifts ==> apply double shift QR |
%----------------------------------------------------% */
h12 = h__[istart + (istart + 1) * h_dim1];
h22 = h__[istart + 1 + (istart + 1) * h_dim1];
h32 = h__[istart + 2 + (istart + 1) * h_dim1];
/* %---------------------------------------------------------%
| Compute 1st column of (H - shift*I)*(H - conj(shift)*I) |
%---------------------------------------------------------% */
s = sigmar * 2.f;
t = igraphdlapy2_(&sigmar, &sigmai);
u[0] = (h11 * (h11 - s) + t * t) / h21 + h12;
u[1] = h11 + h22 - s;
u[2] = h32;
i__2 = iend - 1;
for (i__ = istart; i__ <= i__2; ++i__) {
/* Computing MIN */
i__3 = 3, i__4 = iend - i__ + 1;
nr = min(i__3,i__4);
/* %-----------------------------------------------------%
| Construct Householder reflector G to zero out u(1). |
| G is of the form I - tau*( 1 u )' * ( 1 u' ). |
%-----------------------------------------------------% */
igraphdlarfg_(&nr, u, &u[1], &c__1, &tau);
if (i__ > istart) {
h__[i__ + (i__ - 1) * h_dim1] = u[0];
h__[i__ + 1 + (i__ - 1) * h_dim1] = 0.;
if (i__ < iend - 1) {
h__[i__ + 2 + (i__ - 1) * h_dim1] = 0.;
}
}
u[0] = 1.;
/* %--------------------------------------%
| Apply the reflector to the left of H |
%--------------------------------------% */
i__3 = kplusp - i__ + 1;
igraphdlarf_("Left", &nr, &i__3, u, &c__1, &tau, &h__[i__ + i__ *
h_dim1], ldh, &workl[1]);
/* %---------------------------------------%
| Apply the reflector to the right of H |
%---------------------------------------%
Computing MIN */
i__3 = i__ + 3;
ir = min(i__3,iend);
igraphdlarf_("Right", &ir, &nr, u, &c__1, &tau, &h__[i__ * h_dim1 +
1], ldh, &workl[1]);
/* %-----------------------------------------------------%
| Accumulate the reflector in the matrix Q; Q <- Q*G |
%-----------------------------------------------------% */
igraphdlarf_("Right", &kplusp, &nr, u, &c__1, &tau, &q[i__ * q_dim1
+ 1], ldq, &workl[1]);
/* %----------------------------%
| Prepare for next reflector |
%----------------------------% */
if (i__ < iend - 1) {
u[0] = h__[i__ + 1 + i__ * h_dim1];
u[1] = h__[i__ + 2 + i__ * h_dim1];
if (i__ < iend - 2) {
u[2] = h__[i__ + 3 + i__ * h_dim1];
}
}
/* L90: */
}
/* %--------------------------------------------%
| Finished applying a complex pair of shifts |
| to the current block |
%--------------------------------------------% */
}
L100:
/* %---------------------------------------------------------%
| Apply the same shift to the next block if there is any. |
%---------------------------------------------------------% */
istart = iend + 1;
if (iend < kplusp) {
goto L20;
}
/* %---------------------------------------------%
| Loop back to the top to get the next shift. |
%---------------------------------------------% */
L110:
;
}
/* %--------------------------------------------------%
| Perform a similarity transformation that makes |
| sure that H will have non negative sub diagonals |
%--------------------------------------------------% */
i__1 = *kev;
for (j = 1; j <= i__1; ++j) {
if (h__[j + 1 + j * h_dim1] < 0.) {
i__2 = kplusp - j + 1;
igraphdscal_(&i__2, &c_b43, &h__[j + 1 + j * h_dim1], ldh);
/* Computing MIN */
i__3 = j + 2;
i__2 = min(i__3,kplusp);
igraphdscal_(&i__2, &c_b43, &h__[(j + 1) * h_dim1 + 1], &c__1);
/* Computing MIN */
i__3 = j + *np + 1;
i__2 = min(i__3,kplusp);
igraphdscal_(&i__2, &c_b43, &q[(j + 1) * q_dim1 + 1], &c__1);
}
/* L120: */
}
i__1 = *kev;
for (i__ = 1; i__ <= i__1; ++i__) {
/* %--------------------------------------------%
| Final check for splitting and deflation. |
| Use a standard test as in the QR algorithm |
| REFERENCE: LAPACK subroutine dlahqr |
%--------------------------------------------% */
tst1 = (d__1 = h__[i__ + i__ * h_dim1], abs(d__1)) + (d__2 = h__[i__
+ 1 + (i__ + 1) * h_dim1], abs(d__2));
if (tst1 == 0.) {
tst1 = igraphdlanhs_("1", kev, &h__[h_offset], ldh, &workl[1]);
}
/* Computing MAX */
d__1 = ulp * tst1;
if (h__[i__ + 1 + i__ * h_dim1] <= max(d__1,smlnum)) {
h__[i__ + 1 + i__ * h_dim1] = 0.;
}
/* L130: */
}
/* %-------------------------------------------------%
| Compute the (kev+1)-st column of (V*Q) and |
| temporarily store the result in WORKD(N+1:2*N). |
| This is needed in the residual update since we |
| cannot GUARANTEE that the corresponding entry |
| of H would be zero as in exact arithmetic. |
%-------------------------------------------------% */
if (h__[*kev + 1 + *kev * h_dim1] > 0.) {
igraphdgemv_("N", n, &kplusp, &c_b6, &v[v_offset], ldv, &q[(*kev + 1) *
q_dim1 + 1], &c__1, &c_b5, &workd[*n + 1], &c__1);
}
/* %----------------------------------------------------------%
| Compute column 1 to kev of (V*Q) in backward order |
| taking advantage of the upper Hessenberg structure of Q. |
%----------------------------------------------------------% */
i__1 = *kev;
for (i__ = 1; i__ <= i__1; ++i__) {
i__2 = kplusp - i__ + 1;
igraphdgemv_("N", n, &i__2, &c_b6, &v[v_offset], ldv, &q[(*kev - i__ + 1) *
q_dim1 + 1], &c__1, &c_b5, &workd[1], &c__1);
igraphdcopy_(n, &workd[1], &c__1, &v[(kplusp - i__ + 1) * v_dim1 + 1], &
c__1);
/* L140: */
}
/* %-------------------------------------------------%
| Move v(:,kplusp-kev+1:kplusp) into v(:,1:kev). |
%-------------------------------------------------% */
igraphdlacpy_("A", n, kev, &v[(kplusp - *kev + 1) * v_dim1 + 1], ldv, &v[
v_offset], ldv);
/* %--------------------------------------------------------------%
| Copy the (kev+1)-st column of (V*Q) in the appropriate place |
%--------------------------------------------------------------% */
if (h__[*kev + 1 + *kev * h_dim1] > 0.) {
igraphdcopy_(n, &workd[*n + 1], &c__1, &v[(*kev + 1) * v_dim1 + 1], &c__1);
}
/* %-------------------------------------%
| Update the residual vector: |
| r <- sigmak*r + betak*v(:,kev+1) |
| where |
| sigmak = (e_{kplusp}'*Q)*e_{kev} |
| betak = e_{kev+1}'*H*e_{kev} |
%-------------------------------------% */
igraphdscal_(n, &q[kplusp + *kev * q_dim1], &resid[1], &c__1);
if (h__[*kev + 1 + *kev * h_dim1] > 0.) {
igraphdaxpy_(n, &h__[*kev + 1 + *kev * h_dim1], &v[(*kev + 1) * v_dim1 + 1],
&c__1, &resid[1], &c__1);
}
if (msglvl > 1) {
igraphdvout_(&logfil, &c__1, &q[kplusp + *kev * q_dim1], &ndigit, "_napps:"
" sigmak = (e_{kev+p}^T*Q)*e_{kev}", (ftnlen)40);
igraphdvout_(&logfil, &c__1, &h__[*kev + 1 + *kev * h_dim1], &ndigit, "_na"
"pps: betak = e_{kev+1}^T*H*e_{kev}", (ftnlen)37);
igraphivout_(&logfil, &c__1, kev, &ndigit, "_napps: Order of the final Hes"
"senberg matrix ", (ftnlen)45);
if (msglvl > 2) {
igraphdmout_(&logfil, kev, kev, &h__[h_offset], ldh, &ndigit, "_napps:"
" updated Hessenberg matrix H for next iteration", (ftnlen)
54);
}
}
L9000:
igraphsecond_(&t1);
tnapps += t1 - t0;
return 0;
/* %---------------%
| End of dnapps |
%---------------% */
} /* igraphdnapps_ */
/* Subroutine */ int igraphdlaqr2_(logical *wantt, logical *wantz, integer *n,
integer *ktop, integer *kbot, integer *nw, doublereal *h__, integer *
ldh, integer *iloz, integer *ihiz, doublereal *z__, integer *ldz,
integer *ns, integer *nd, doublereal *sr, doublereal *si, doublereal *
v, integer *ldv, integer *nh, doublereal *t, integer *ldt, integer *
nv, doublereal *wv, integer *ldwv, doublereal *work, integer *lwork)
{
/* System generated locals */
integer h_dim1, h_offset, t_dim1, t_offset, v_dim1, v_offset, wv_dim1,
wv_offset, z_dim1, z_offset, i__1, i__2, i__3, i__4;
doublereal d__1, d__2, d__3, d__4, d__5, d__6;
/* Builtin functions */
double sqrt(doublereal);
/* Local variables */
integer i__, j, k;
doublereal s, aa, bb, cc, dd, cs, sn;
integer jw;
doublereal evi, evk, foo;
integer kln;
doublereal tau, ulp;
integer lwk1, lwk2;
doublereal beta;
integer kend, kcol, info, ifst, ilst, ltop, krow;
extern /* Subroutine */ int igraphdlarf_(char *, integer *, integer *,
doublereal *, integer *, doublereal *, doublereal *, integer *,
doublereal *), igraphdgemm_(char *, char *, integer *, integer *
, integer *, doublereal *, doublereal *, integer *, doublereal *,
integer *, doublereal *, doublereal *, integer *);
logical bulge;
extern /* Subroutine */ int igraphdcopy_(integer *, doublereal *, integer *,
doublereal *, integer *);
integer infqr, kwtop;
extern /* Subroutine */ int igraphdlanv2_(doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *,
doublereal *, doublereal *, doublereal *, doublereal *), igraphdlabad_(
doublereal *, doublereal *);
extern doublereal igraphdlamch_(char *);
extern /* Subroutine */ int igraphdgehrd_(integer *, integer *, integer *,
doublereal *, integer *, doublereal *, doublereal *, integer *,
integer *), igraphdlarfg_(integer *, doublereal *, doublereal *,
integer *, doublereal *), igraphdlahqr_(logical *, logical *, integer *,
integer *, integer *, doublereal *, integer *, doublereal *,
doublereal *, integer *, integer *, doublereal *, integer *,
integer *), igraphdlacpy_(char *, integer *, integer *, doublereal *,
integer *, doublereal *, integer *);
doublereal safmin;
extern /* Subroutine */ int igraphdlaset_(char *, integer *, integer *,
doublereal *, doublereal *, doublereal *, integer *);
doublereal safmax;
extern /* Subroutine */ int igraphdtrexc_(char *, integer *, doublereal *,
integer *, doublereal *, integer *, integer *, integer *,
doublereal *, integer *), igraphdormhr_(char *, char *, integer
*, integer *, integer *, integer *, doublereal *, integer *,
doublereal *, doublereal *, integer *, doublereal *, integer *,
integer *);
logical sorted;
doublereal smlnum;
integer lwkopt;
/* -- LAPACK auxiliary routine (version 3.2.2) --
Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..
-- June 2010 --
This subroutine is identical to DLAQR3 except that it avoids
recursion by calling DLAHQR instead of DLAQR4.
******************************************************************
Aggressive early deflation:
This subroutine accepts as input an upper Hessenberg matrix
H and performs an orthogonal similarity transformation
designed to detect and deflate fully converged eigenvalues from
a trailing principal submatrix. On output H has been over-
written by a new Hessenberg matrix that is a perturbation of
an orthogonal similarity transformation of H. It is to be
hoped that the final version of H has many zero subdiagonal
entries.
******************************************************************
WANTT (input) LOGICAL
If .TRUE., then the Hessenberg matrix H is fully updated
so that the quasi-triangular Schur factor may be
computed (in cooperation with the calling subroutine).
If .FALSE., then only enough of H is updated to preserve
the eigenvalues.
WANTZ (input) LOGICAL
If .TRUE., then the orthogonal matrix Z is updated so
so that the orthogonal Schur factor may be computed
(in cooperation with the calling subroutine).
If .FALSE., then Z is not referenced.
N (input) INTEGER
The order of the matrix H and (if WANTZ is .TRUE.) the
order of the orthogonal matrix Z.
KTOP (input) INTEGER
It is assumed that either KTOP = 1 or H(KTOP,KTOP-1)=0.
KBOT and KTOP together determine an isolated block
along the diagonal of the Hessenberg matrix.
KBOT (input) INTEGER
It is assumed without a check that either
KBOT = N or H(KBOT+1,KBOT)=0. KBOT and KTOP together
determine an isolated block along the diagonal of the
Hessenberg matrix.
NW (input) INTEGER
Deflation window size. 1 .LE. NW .LE. (KBOT-KTOP+1).
H (input/output) DOUBLE PRECISION array, dimension (LDH,N)
On input the initial N-by-N section of H stores the
Hessenberg matrix undergoing aggressive early deflation.
On output H has been transformed by an orthogonal
similarity transformation, perturbed, and the returned
to Hessenberg form that (it is to be hoped) has some
zero subdiagonal entries.
LDH (input) integer
Leading dimension of H just as declared in the calling
subroutine. N .LE. LDH
ILOZ (input) INTEGER
IHIZ (input) INTEGER
Specify the rows of Z to which transformations must be
applied if WANTZ is .TRUE.. 1 .LE. ILOZ .LE. IHIZ .LE. N.
Z (input/output) DOUBLE PRECISION array, dimension (LDZ,N)
IF WANTZ is .TRUE., then on output, the orthogonal
similarity transformation mentioned above has been
accumulated into Z(ILOZ:IHIZ,ILO:IHI) from the right.
If WANTZ is .FALSE., then Z is unreferenced.
LDZ (input) integer
The leading dimension of Z just as declared in the
calling subroutine. 1 .LE. LDZ.
NS (output) integer
The number of unconverged (ie approximate) eigenvalues
returned in SR and SI that may be used as shifts by the
calling subroutine.
ND (output) integer
The number of converged eigenvalues uncovered by this
subroutine.
SR (output) DOUBLE PRECISION array, dimension (KBOT)
SI (output) DOUBLE PRECISION array, dimension (KBOT)
On output, the real and imaginary parts of approximate
eigenvalues that may be used for shifts are stored in
SR(KBOT-ND-NS+1) through SR(KBOT-ND) and
SI(KBOT-ND-NS+1) through SI(KBOT-ND), respectively.
The real and imaginary parts of converged eigenvalues
are stored in SR(KBOT-ND+1) through SR(KBOT) and
SI(KBOT-ND+1) through SI(KBOT), respectively.
V (workspace) DOUBLE PRECISION array, dimension (LDV,NW)
An NW-by-NW work array.
LDV (input) integer scalar
The leading dimension of V just as declared in the
calling subroutine. NW .LE. LDV
NH (input) integer scalar
The number of columns of T. NH.GE.NW.
T (workspace) DOUBLE PRECISION array, dimension (LDT,NW)
LDT (input) integer
The leading dimension of T just as declared in the
calling subroutine. NW .LE. LDT
NV (input) integer
The number of rows of work array WV available for
workspace. NV.GE.NW.
WV (workspace) DOUBLE PRECISION array, dimension (LDWV,NW)
LDWV (input) integer
The leading dimension of W just as declared in the
calling subroutine. NW .LE. LDV
WORK (workspace) DOUBLE PRECISION array, dimension (LWORK)
On exit, WORK(1) is set to an estimate of the optimal value
of LWORK for the given values of N, NW, KTOP and KBOT.
LWORK (input) integer
The dimension of the work array WORK. LWORK = 2*NW
suffices, but greater efficiency may result from larger
values of LWORK.
If LWORK = -1, then a workspace query is assumed; DLAQR2
only estimates the optimal workspace size for the given
values of N, NW, KTOP and KBOT. The estimate is returned
in WORK(1). No error message related to LWORK is issued
by XERBLA. Neither H nor Z are accessed.
================================================================
Based on contributions by
Karen Braman and Ralph Byers, Department of Mathematics,
University of Kansas, USA
================================================================
==== Estimate optimal workspace. ====
Parameter adjustments */
h_dim1 = *ldh;
h_offset = 1 + h_dim1;
h__ -= h_offset;
z_dim1 = *ldz;
z_offset = 1 + z_dim1;
z__ -= z_offset;
--sr;
--si;
v_dim1 = *ldv;
v_offset = 1 + v_dim1;
v -= v_offset;
t_dim1 = *ldt;
t_offset = 1 + t_dim1;
t -= t_offset;
wv_dim1 = *ldwv;
wv_offset = 1 + wv_dim1;
wv -= wv_offset;
--work;
/* Function Body
Computing MIN */
i__1 = *nw, i__2 = *kbot - *ktop + 1;
jw = min(i__1,i__2);
if (jw <= 2) {
lwkopt = 1;
} else {
/* ==== Workspace query call to DGEHRD ==== */
i__1 = jw - 1;
igraphdgehrd_(&jw, &c__1, &i__1, &t[t_offset], ldt, &work[1], &work[1], &
c_n1, &info);
lwk1 = (integer) work[1];
/* ==== Workspace query call to DORMHR ==== */
i__1 = jw - 1;
igraphdormhr_("R", "N", &jw, &jw, &c__1, &i__1, &t[t_offset], ldt, &work[1],
&v[v_offset], ldv, &work[1], &c_n1, &info);
lwk2 = (integer) work[1];
/* ==== Optimal workspace ==== */
lwkopt = jw + max(lwk1,lwk2);
}
/* ==== Quick return in case of workspace query. ==== */
if (*lwork == -1) {
work[1] = (doublereal) lwkopt;
return 0;
}
/* ==== Nothing to do ...
... for an empty active block ... ==== */
*ns = 0;
*nd = 0;
work[1] = 1.;
if (*ktop > *kbot) {
return 0;
}
/* ... nor for an empty deflation window. ==== */
if (*nw < 1) {
return 0;
}
/* ==== Machine constants ==== */
safmin = igraphdlamch_("SAFE MINIMUM");
safmax = 1. / safmin;
igraphdlabad_(&safmin, &safmax);
ulp = igraphdlamch_("PRECISION");
smlnum = safmin * ((doublereal) (*n) / ulp);
/* ==== Setup deflation window ====
Computing MIN */
i__1 = *nw, i__2 = *kbot - *ktop + 1;
jw = min(i__1,i__2);
kwtop = *kbot - jw + 1;
if (kwtop == *ktop) {
s = 0.;
} else {
s = h__[kwtop + (kwtop - 1) * h_dim1];
}
if (*kbot == kwtop) {
/* ==== 1-by-1 deflation window: not much to do ==== */
sr[kwtop] = h__[kwtop + kwtop * h_dim1];
si[kwtop] = 0.;
*ns = 1;
*nd = 0;
/* Computing MAX */
d__2 = smlnum, d__3 = ulp * (d__1 = h__[kwtop + kwtop * h_dim1], abs(
d__1));
if (abs(s) <= max(d__2,d__3)) {
*ns = 0;
*nd = 1;
if (kwtop > *ktop) {
h__[kwtop + (kwtop - 1) * h_dim1] = 0.;
}
}
work[1] = 1.;
return 0;
}
/* ==== Convert to spike-triangular form. (In case of a
. rare QR failure, this routine continues to do
. aggressive early deflation using that part of
. the deflation window that converged using INFQR
. here and there to keep track.) ==== */
igraphdlacpy_("U", &jw, &jw, &h__[kwtop + kwtop * h_dim1], ldh, &t[t_offset],
ldt);
i__1 = jw - 1;
i__2 = *ldh + 1;
i__3 = *ldt + 1;
igraphdcopy_(&i__1, &h__[kwtop + 1 + kwtop * h_dim1], &i__2, &t[t_dim1 + 2], &
i__3);
igraphdlaset_("A", &jw, &jw, &c_b12, &c_b13, &v[v_offset], ldv);
igraphdlahqr_(&c_true, &c_true, &jw, &c__1, &jw, &t[t_offset], ldt, &sr[kwtop],
&si[kwtop], &c__1, &jw, &v[v_offset], ldv, &infqr);
/* ==== DTREXC needs a clean margin near the diagonal ==== */
i__1 = jw - 3;
for (j = 1; j <= i__1; ++j) {
t[j + 2 + j * t_dim1] = 0.;
t[j + 3 + j * t_dim1] = 0.;
/* L10: */
}
if (jw > 2) {
t[jw + (jw - 2) * t_dim1] = 0.;
}
/* ==== Deflation detection loop ==== */
*ns = jw;
ilst = infqr + 1;
L20:
if (ilst <= *ns) {
if (*ns == 1) {
bulge = FALSE_;
} else {
bulge = t[*ns + (*ns - 1) * t_dim1] != 0.;
}
/* ==== Small spike tip test for deflation ==== */
if (! bulge) {
/* ==== Real eigenvalue ==== */
foo = (d__1 = t[*ns + *ns * t_dim1], abs(d__1));
if (foo == 0.) {
foo = abs(s);
}
/* Computing MAX */
d__2 = smlnum, d__3 = ulp * foo;
if ((d__1 = s * v[*ns * v_dim1 + 1], abs(d__1)) <= max(d__2,d__3))
{
/* ==== Deflatable ==== */
--(*ns);
} else {
/* ==== Undeflatable. Move it up out of the way.
. (DTREXC can not fail in this case.) ==== */
ifst = *ns;
igraphdtrexc_("V", &jw, &t[t_offset], ldt, &v[v_offset], ldv, &ifst,
&ilst, &work[1], &info);
++ilst;
}
} else {
/* ==== Complex conjugate pair ==== */
foo = (d__3 = t[*ns + *ns * t_dim1], abs(d__3)) + sqrt((d__1 = t[*
ns + (*ns - 1) * t_dim1], abs(d__1))) * sqrt((d__2 = t[*
ns - 1 + *ns * t_dim1], abs(d__2)));
if (foo == 0.) {
foo = abs(s);
}
/* Computing MAX */
d__3 = (d__1 = s * v[*ns * v_dim1 + 1], abs(d__1)), d__4 = (d__2 =
s * v[(*ns - 1) * v_dim1 + 1], abs(d__2));
/* Computing MAX */
d__5 = smlnum, d__6 = ulp * foo;
if (max(d__3,d__4) <= max(d__5,d__6)) {
/* ==== Deflatable ==== */
*ns += -2;
} else {
/* ==== Undeflatable. Move them up out of the way.
. Fortunately, DTREXC does the right thing with
. ILST in case of a rare exchange failure. ==== */
ifst = *ns;
igraphdtrexc_("V", &jw, &t[t_offset], ldt, &v[v_offset], ldv, &ifst,
&ilst, &work[1], &info);
ilst += 2;
}
}
/* ==== End deflation detection loop ==== */
goto L20;
}
/* ==== Return to Hessenberg form ==== */
if (*ns == 0) {
s = 0.;
}
if (*ns < jw) {
/* ==== sorting diagonal blocks of T improves accuracy for
. graded matrices. Bubble sort deals well with
. exchange failures. ==== */
sorted = FALSE_;
i__ = *ns + 1;
L30:
if (sorted) {
goto L50;
}
sorted = TRUE_;
kend = i__ - 1;
i__ = infqr + 1;
if (i__ == *ns) {
k = i__ + 1;
} else if (t[i__ + 1 + i__ * t_dim1] == 0.) {
k = i__ + 1;
} else {
k = i__ + 2;
}
L40:
if (k <= kend) {
if (k == i__ + 1) {
evi = (d__1 = t[i__ + i__ * t_dim1], abs(d__1));
} else {
evi = (d__3 = t[i__ + i__ * t_dim1], abs(d__3)) + sqrt((d__1 =
t[i__ + 1 + i__ * t_dim1], abs(d__1))) * sqrt((d__2 =
t[i__ + (i__ + 1) * t_dim1], abs(d__2)));
}
if (k == kend) {
evk = (d__1 = t[k + k * t_dim1], abs(d__1));
} else if (t[k + 1 + k * t_dim1] == 0.) {
evk = (d__1 = t[k + k * t_dim1], abs(d__1));
} else {
evk = (d__3 = t[k + k * t_dim1], abs(d__3)) + sqrt((d__1 = t[
k + 1 + k * t_dim1], abs(d__1))) * sqrt((d__2 = t[k +
(k + 1) * t_dim1], abs(d__2)));
}
if (evi >= evk) {
i__ = k;
} else {
sorted = FALSE_;
ifst = i__;
ilst = k;
igraphdtrexc_("V", &jw, &t[t_offset], ldt, &v[v_offset], ldv, &ifst,
&ilst, &work[1], &info);
if (info == 0) {
i__ = ilst;
} else {
i__ = k;
}
}
if (i__ == kend) {
k = i__ + 1;
} else if (t[i__ + 1 + i__ * t_dim1] == 0.) {
k = i__ + 1;
} else {
k = i__ + 2;
}
goto L40;
}
goto L30;
L50:
;
}
/* ==== Restore shift/eigenvalue array from T ==== */
i__ = jw;
L60:
if (i__ >= infqr + 1) {
if (i__ == infqr + 1) {
sr[kwtop + i__ - 1] = t[i__ + i__ * t_dim1];
si[kwtop + i__ - 1] = 0.;
--i__;
} else if (t[i__ + (i__ - 1) * t_dim1] == 0.) {
sr[kwtop + i__ - 1] = t[i__ + i__ * t_dim1];
si[kwtop + i__ - 1] = 0.;
--i__;
} else {
aa = t[i__ - 1 + (i__ - 1) * t_dim1];
cc = t[i__ + (i__ - 1) * t_dim1];
bb = t[i__ - 1 + i__ * t_dim1];
dd = t[i__ + i__ * t_dim1];
igraphdlanv2_(&aa, &bb, &cc, &dd, &sr[kwtop + i__ - 2], &si[kwtop + i__
- 2], &sr[kwtop + i__ - 1], &si[kwtop + i__ - 1], &cs, &
sn);
i__ += -2;
}
goto L60;
}
if (*ns < jw || s == 0.) {
if (*ns > 1 && s != 0.) {
/* ==== Reflect spike back into lower triangle ==== */
igraphdcopy_(ns, &v[v_offset], ldv, &work[1], &c__1);
beta = work[1];
igraphdlarfg_(ns, &beta, &work[2], &c__1, &tau);
work[1] = 1.;
i__1 = jw - 2;
i__2 = jw - 2;
igraphdlaset_("L", &i__1, &i__2, &c_b12, &c_b12, &t[t_dim1 + 3], ldt);
igraphdlarf_("L", ns, &jw, &work[1], &c__1, &tau, &t[t_offset], ldt, &
work[jw + 1]);
igraphdlarf_("R", ns, ns, &work[1], &c__1, &tau, &t[t_offset], ldt, &
work[jw + 1]);
igraphdlarf_("R", &jw, ns, &work[1], &c__1, &tau, &v[v_offset], ldv, &
work[jw + 1]);
i__1 = *lwork - jw;
igraphdgehrd_(&jw, &c__1, ns, &t[t_offset], ldt, &work[1], &work[jw + 1]
, &i__1, &info);
}
/* ==== Copy updated reduced window into place ==== */
if (kwtop > 1) {
h__[kwtop + (kwtop - 1) * h_dim1] = s * v[v_dim1 + 1];
}
igraphdlacpy_("U", &jw, &jw, &t[t_offset], ldt, &h__[kwtop + kwtop * h_dim1]
, ldh);
i__1 = jw - 1;
i__2 = *ldt + 1;
i__3 = *ldh + 1;
igraphdcopy_(&i__1, &t[t_dim1 + 2], &i__2, &h__[kwtop + 1 + kwtop * h_dim1],
&i__3);
/* ==== Accumulate orthogonal matrix in order update
. H and Z, if requested. ==== */
if (*ns > 1 && s != 0.) {
i__1 = *lwork - jw;
igraphdormhr_("R", "N", &jw, ns, &c__1, ns, &t[t_offset], ldt, &work[1],
&v[v_offset], ldv, &work[jw + 1], &i__1, &info);
}
/* ==== Update vertical slab in H ==== */
if (*wantt) {
ltop = 1;
} else {
ltop = *ktop;
}
i__1 = kwtop - 1;
i__2 = *nv;
for (krow = ltop; i__2 < 0 ? krow >= i__1 : krow <= i__1; krow +=
i__2) {
/* Computing MIN */
i__3 = *nv, i__4 = kwtop - krow;
kln = min(i__3,i__4);
igraphdgemm_("N", "N", &kln, &jw, &jw, &c_b13, &h__[krow + kwtop *
h_dim1], ldh, &v[v_offset], ldv, &c_b12, &wv[wv_offset],
ldwv);
igraphdlacpy_("A", &kln, &jw, &wv[wv_offset], ldwv, &h__[krow + kwtop *
h_dim1], ldh);
/* L70: */
}
/* ==== Update horizontal slab in H ==== */
if (*wantt) {
i__2 = *n;
i__1 = *nh;
for (kcol = *kbot + 1; i__1 < 0 ? kcol >= i__2 : kcol <= i__2;
kcol += i__1) {
/* Computing MIN */
i__3 = *nh, i__4 = *n - kcol + 1;
kln = min(i__3,i__4);
igraphdgemm_("C", "N", &jw, &kln, &jw, &c_b13, &v[v_offset], ldv, &
h__[kwtop + kcol * h_dim1], ldh, &c_b12, &t[t_offset],
ldt);
igraphdlacpy_("A", &jw, &kln, &t[t_offset], ldt, &h__[kwtop + kcol *
h_dim1], ldh);
/* L80: */
}
}
/* ==== Update vertical slab in Z ==== */
if (*wantz) {
i__1 = *ihiz;
i__2 = *nv;
for (krow = *iloz; i__2 < 0 ? krow >= i__1 : krow <= i__1; krow +=
i__2) {
/* Computing MIN */
i__3 = *nv, i__4 = *ihiz - krow + 1;
kln = min(i__3,i__4);
igraphdgemm_("N", "N", &kln, &jw, &jw, &c_b13, &z__[krow + kwtop *
z_dim1], ldz, &v[v_offset], ldv, &c_b12, &wv[
wv_offset], ldwv);
igraphdlacpy_("A", &kln, &jw, &wv[wv_offset], ldwv, &z__[krow +
kwtop * z_dim1], ldz);
/* L90: */
}
}
}
/* ==== Return the number of deflations ... ==== */
*nd = jw - *ns;
/* ==== ... and the number of shifts. (Subtracting
. INFQR from the spike length takes care
. of the case of a rare QR failure while
. calculating eigenvalues of the deflation
. window.) ==== */
*ns -= infqr;
/* ==== Return optimal workspace. ==== */
work[1] = (doublereal) lwkopt;
/* ==== End of DLAQR2 ==== */
return 0;
} /* igraphdlaqr2_ */
/* Subroutine */ int igraphdorm2l_(char *side, char *trans, integer *m, integer *n,
integer *k, doublereal *a, integer *lda, doublereal *tau, doublereal *
c__, integer *ldc, doublereal *work, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, c_dim1, c_offset, i__1, i__2;
/* Local variables */
integer i__, i1, i2, i3, mi, ni, nq;
doublereal aii;
logical left;
extern /* Subroutine */ int igraphdlarf_(char *, integer *, integer *,
doublereal *, integer *, doublereal *, doublereal *, integer *,
doublereal *);
extern logical igraphlsame_(char *, char *);
extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);
logical notran;
/* -- LAPACK routine (version 3.3.1) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
-- April 2011 --
Purpose
=======
DORM2L overwrites the general real m by n matrix C with
Q * C if SIDE = 'L' and TRANS = 'N', or
Q**T * C if SIDE = 'L' and TRANS = 'T', or
C * Q if SIDE = 'R' and TRANS = 'N', or
C * Q**T if SIDE = 'R' and TRANS = 'T',
where Q is a real orthogonal matrix defined as the product of k
elementary reflectors
Q = H(k) . . . H(2) H(1)
as returned by DGEQLF. Q is of order m if SIDE = 'L' and of order n
if SIDE = 'R'.
Arguments
=========
SIDE (input) CHARACTER*1
= 'L': apply Q or Q**T from the Left
= 'R': apply Q or Q**T from the Right
TRANS (input) CHARACTER*1
= 'N': apply Q (No transpose)
= 'T': apply Q**T (Transpose)
M (input) INTEGER
The number of rows of the matrix C. M >= 0.
N (input) INTEGER
The number of columns of the matrix C. N >= 0.
K (input) INTEGER
The number of elementary reflectors whose product defines
the matrix Q.
If SIDE = 'L', M >= K >= 0;
if SIDE = 'R', N >= K >= 0.
A (input) DOUBLE PRECISION array, dimension (LDA,K)
The i-th column must contain the vector which defines the
elementary reflector H(i), for i = 1,2,...,k, as returned by
DGEQLF in the last k columns of its array argument A.
A is modified by the routine but restored on exit.
LDA (input) INTEGER
The leading dimension of the array A.
If SIDE = 'L', LDA >= max(1,M);
if SIDE = 'R', LDA >= max(1,N).
TAU (input) DOUBLE PRECISION array, dimension (K)
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by DGEQLF.
C (input/output) DOUBLE PRECISION array, dimension (LDC,N)
On entry, the m by n matrix C.
On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.
LDC (input) INTEGER
The leading dimension of the array C. LDC >= max(1,M).
WORK (workspace) DOUBLE PRECISION array, dimension
(N) if SIDE = 'L',
(M) if SIDE = 'R'
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
=====================================================================
Test the input arguments
Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--tau;
c_dim1 = *ldc;
c_offset = 1 + c_dim1;
c__ -= c_offset;
--work;
/* Function Body */
*info = 0;
left = igraphlsame_(side, "L");
notran = igraphlsame_(trans, "N");
/* NQ is the order of Q */
if (left) {
nq = *m;
} else {
nq = *n;
}
if (! left && ! igraphlsame_(side, "R")) {
*info = -1;
} else if (! notran && ! igraphlsame_(trans, "T")) {
*info = -2;
} else if (*m < 0) {
*info = -3;
} else if (*n < 0) {
*info = -4;
} else if (*k < 0 || *k > nq) {
*info = -5;
} else if (*lda < max(1,nq)) {
*info = -7;
} else if (*ldc < max(1,*m)) {
*info = -10;
}
if (*info != 0) {
i__1 = -(*info);
igraphxerbla_("DORM2L", &i__1, (ftnlen)6);
return 0;
}
/* Quick return if possible */
if (*m == 0 || *n == 0 || *k == 0) {
return 0;
}
if (left && notran || ! left && ! notran) {
i1 = 1;
i2 = *k;
i3 = 1;
} else {
i1 = *k;
i2 = 1;
i3 = -1;
}
if (left) {
ni = *n;
} else {
mi = *m;
}
i__1 = i2;
i__2 = i3;
for (i__ = i1; i__2 < 0 ? i__ >= i__1 : i__ <= i__1; i__ += i__2) {
if (left) {
/* H(i) is applied to C(1:m-k+i,1:n) */
mi = *m - *k + i__;
} else {
/* H(i) is applied to C(1:m,1:n-k+i) */
ni = *n - *k + i__;
}
/* Apply H(i) */
aii = a[nq - *k + i__ + i__ * a_dim1];
a[nq - *k + i__ + i__ * a_dim1] = 1.;
igraphdlarf_(side, &mi, &ni, &a[i__ * a_dim1 + 1], &c__1, &tau[i__], &c__[
c_offset], ldc, &work[1]);
a[nq - *k + i__ + i__ * a_dim1] = aii;
/* L10: */
}
return 0;
/* End of DORM2L */
} /* igraphdorm2l_ */
/* Subroutine */ int igraphdgehd2_(integer *n, integer *ilo, integer *ihi,
doublereal *a, integer *lda, doublereal *tau, doublereal *work,
integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
/* Local variables */
integer i__;
doublereal aii;
extern /* Subroutine */ int igraphdlarf_(char *, integer *, integer *,
doublereal *, integer *, doublereal *, doublereal *, integer *,
doublereal *), igraphdlarfg_(integer *, doublereal *,
doublereal *, integer *, doublereal *), igraphxerbla_(char *, integer *,
ftnlen);
/* -- LAPACK routine (version 3.3.1) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
-- April 2011 --
Purpose
=======
DGEHD2 reduces a real general matrix A to upper Hessenberg form H by
an orthogonal similarity transformation: Q**T * A * Q = H .
Arguments
=========
N (input) INTEGER
The order of the matrix A. N >= 0.
ILO (input) INTEGER
IHI (input) INTEGER
It is assumed that A is already upper triangular in rows
and columns 1:ILO-1 and IHI+1:N. ILO and IHI are normally
set by a previous call to DGEBAL; otherwise they should be
set to 1 and N respectively. See Further Details.
1 <= ILO <= IHI <= max(1,N).
A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the n by n general matrix to be reduced.
On exit, the upper triangle and the first subdiagonal of A
are overwritten with the upper Hessenberg matrix H, and the
elements below the first subdiagonal, with the array TAU,
represent the orthogonal matrix Q as a product of elementary
reflectors. See Further Details.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
TAU (output) DOUBLE PRECISION array, dimension (N-1)
The scalar factors of the elementary reflectors (see Further
Details).
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
===============
The matrix Q is represented as a product of (ihi-ilo) elementary
reflectors
Q = H(ilo) H(ilo+1) . . . H(ihi-1).
Each H(i) has the form
H(i) = I - tau * v * v**T
where tau is a real scalar, and v is a real vector with
v(1:i) = 0, v(i+1) = 1 and v(ihi+1:n) = 0; v(i+2:ihi) is stored on
exit in A(i+2:ihi,i), and tau in TAU(i).
The contents of A are illustrated by the following example, with
n = 7, ilo = 2 and ihi = 6:
on entry, on exit,
( a a a a a a a ) ( a a h h h h a )
( a a a a a a ) ( a h h h h a )
( a a a a a a ) ( h h h h h h )
( a a a a a a ) ( v2 h h h h h )
( a a a a a a ) ( v2 v3 h h h h )
( a a a a a a ) ( v2 v3 v4 h h h )
( a ) ( a )
where a denotes an element of the original matrix A, h denotes a
modified element of the upper Hessenberg matrix H, and vi denotes an
element of the vector defining H(i).
=====================================================================
Test the input parameters
Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--tau;
--work;
/* Function Body */
*info = 0;
if (*n < 0) {
*info = -1;
} else if (*ilo < 1 || *ilo > max(1,*n)) {
*info = -2;
} else if (*ihi < min(*ilo,*n) || *ihi > *n) {
*info = -3;
} else if (*lda < max(1,*n)) {
*info = -5;
}
if (*info != 0) {
i__1 = -(*info);
igraphxerbla_("DGEHD2", &i__1, (ftnlen)6);
return 0;
}
i__1 = *ihi - 1;
for (i__ = *ilo; i__ <= i__1; ++i__) {
/* Compute elementary reflector H(i) to annihilate A(i+2:ihi,i) */
i__2 = *ihi - i__;
/* Computing MIN */
i__3 = i__ + 2;
igraphdlarfg_(&i__2, &a[i__ + 1 + i__ * a_dim1], &a[min(i__3,*n) + i__ *
a_dim1], &c__1, &tau[i__]);
aii = a[i__ + 1 + i__ * a_dim1];
a[i__ + 1 + i__ * a_dim1] = 1.;
/* Apply H(i) to A(1:ihi,i+1:ihi) from the right */
i__2 = *ihi - i__;
igraphdlarf_("Right", ihi, &i__2, &a[i__ + 1 + i__ * a_dim1], &c__1, &tau[
i__], &a[(i__ + 1) * a_dim1 + 1], lda, &work[1]);
/* Apply H(i) to A(i+1:ihi,i+1:n) from the left */
i__2 = *ihi - i__;
i__3 = *n - i__;
igraphdlarf_("Left", &i__2, &i__3, &a[i__ + 1 + i__ * a_dim1], &c__1, &tau[
i__], &a[i__ + 1 + (i__ + 1) * a_dim1], lda, &work[1]);
a[i__ + 1 + i__ * a_dim1] = aii;
/* L10: */
}
return 0;
/* End of DGEHD2 */
} /* igraphdgehd2_ */
/* Subroutine */ int igraphdgeqr2_(integer *m, integer *n, doublereal *a, integer *
lda, doublereal *tau, doublereal *work, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
/* Local variables */
static integer i__, k;
static doublereal aii;
extern /* Subroutine */ int igraphdlarf_(char *, integer *, integer *,
doublereal *, integer *, doublereal *, doublereal *, integer *,
doublereal *), igraphdlarfg_(integer *, doublereal *,
doublereal *, integer *, doublereal *), igraphxerbla_(char *, integer *);
/* -- LAPACK routine (version 3.0) -- */
/* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/* Courant Institute, Argonne National Lab, and Rice University */
/* February 29, 1992 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DGEQR2 computes a QR factorization of a real m by n matrix A: */
/* A = Q * R. */
/* Arguments */
/* ========= */
/* M (input) INTEGER */
/* The number of rows of the matrix A. M >= 0. */
/* N (input) INTEGER */
/* The number of columns of the matrix A. N >= 0. */
/* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
/* On entry, the m by n matrix A. */
/* On exit, the elements on and above the diagonal of the array */
/* contain the min(m,n) by n upper trapezoidal matrix R (R is */
/* upper triangular if m >= n); the elements below the diagonal, */
/* with the array TAU, represent the orthogonal matrix Q as a */
/* product of elementary reflectors (see Further Details). */
/* LDA (input) INTEGER */
/* The leading dimension of the array A. LDA >= max(1,M). */
/* TAU (output) DOUBLE PRECISION array, dimension (min(M,N)) */
/* The scalar factors of the elementary reflectors (see Further */
/* Details). */
/* 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 */
/* =============== */
/* The matrix Q is represented as a product of elementary reflectors */
/* Q = H(1) H(2) . . . H(k), where k = min(m,n). */
/* Each H(i) has the form */
/* H(i) = I - tau * v * v' */
/* where tau is a real scalar, and v is a real vector with */
/* v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i), */
/* and tau in TAU(i). */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input arguments */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--tau;
--work;
/* Function Body */
*info = 0;
if (*m < 0) {
*info = -1;
} else if (*n < 0) {
*info = -2;
} else if (*lda < max(1,*m)) {
*info = -4;
}
if (*info != 0) {
i__1 = -(*info);
igraphxerbla_("DGEQR2", &i__1);
return 0;
}
k = min(*m,*n);
i__1 = k;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Generate elementary reflector H(i) to annihilate A(i+1:m,i) */
i__2 = *m - i__ + 1;
/* Computing MIN */
i__3 = i__ + 1;
igraphdlarfg_(&i__2, &a[i__ + i__ * a_dim1], &a[min(i__3,*m) + i__ * a_dim1]
, &c__1, &tau[i__]);
if (i__ < *n) {
/* Apply H(i) to A(i:m,i+1:n) from the left */
aii = a[i__ + i__ * a_dim1];
a[i__ + i__ * a_dim1] = 1.;
i__2 = *m - i__ + 1;
i__3 = *n - i__;
igraphdlarf_("Left", &i__2, &i__3, &a[i__ + i__ * a_dim1], &c__1, &tau[
i__], &a[i__ + (i__ + 1) * a_dim1], lda, &work[1]);
a[i__ + i__ * a_dim1] = aii;
}
/* L10: */
}
return 0;
/* End of DGEQR2 */
} /* igraphdgeqr2_ */
