Add graph references
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+484
@@ -0,0 +1,484 @@
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/* -- translated by f2c (version 20240504).
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You must link the resulting object file with libf2c:
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on Microsoft Windows system, link with libf2c.lib;
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on Linux or Unix systems, link with .../path/to/libf2c.a -lm
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or, if you install libf2c.a in a standard place, with -lf2c -lm
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-- in that order, at the end of the command line, as in
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cc *.o -lf2c -lm
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Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
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http://www.netlib.org/f2c/libf2c.zip
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*/
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#include "f2c.h"
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/* > \brief \b DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous
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transform. Used by sbdsqr.
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=========== DOCUMENTATION ===========
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Online html documentation available at
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http://www.netlib.org/lapack/explore-html/
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> \htmlonly
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> Download DLASQ4 + dependencies
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlasq4.
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f">
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> [TGZ]</a>
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlasq4.
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f">
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> [ZIP]</a>
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlasq4.
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f">
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> [TXT]</a>
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> \endhtmlonly
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Definition:
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===========
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SUBROUTINE DLASQ4( I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN,
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DN1, DN2, TAU, TTYPE, G )
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INTEGER I0, N0, N0IN, PP, TTYPE
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DOUBLE PRECISION DMIN, DMIN1, DMIN2, DN, DN1, DN2, G, TAU
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DOUBLE PRECISION Z( * )
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> \par Purpose:
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=============
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>
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> \verbatim
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>
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> DLASQ4 computes an approximation TAU to the smallest eigenvalue
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> using values of d from the previous transform.
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> \endverbatim
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Arguments:
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==========
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> \param[in] I0
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> \verbatim
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> I0 is INTEGER
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> First index.
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> \endverbatim
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>
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> \param[in] N0
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> \verbatim
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> N0 is INTEGER
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> Last index.
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> \endverbatim
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>
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> \param[in] Z
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> \verbatim
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> Z is DOUBLE PRECISION array, dimension ( 4*N )
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> Z holds the qd array.
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> \endverbatim
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>
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> \param[in] PP
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> \verbatim
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> PP is INTEGER
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> PP=0 for ping, PP=1 for pong.
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> \endverbatim
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>
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> \param[in] N0IN
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> \verbatim
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> N0IN is INTEGER
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> The value of N0 at start of EIGTEST.
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> \endverbatim
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>
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> \param[in] DMIN
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> \verbatim
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> DMIN is DOUBLE PRECISION
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> Minimum value of d.
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> \endverbatim
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>
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> \param[in] DMIN1
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> \verbatim
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> DMIN1 is DOUBLE PRECISION
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> Minimum value of d, excluding D( N0 ).
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> \endverbatim
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>
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> \param[in] DMIN2
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> \verbatim
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> DMIN2 is DOUBLE PRECISION
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> Minimum value of d, excluding D( N0 ) and D( N0-1 ).
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> \endverbatim
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>
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> \param[in] DN
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> \verbatim
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> DN is DOUBLE PRECISION
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> d(N)
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> \endverbatim
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>
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> \param[in] DN1
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> \verbatim
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> DN1 is DOUBLE PRECISION
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> d(N-1)
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> \endverbatim
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>
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> \param[in] DN2
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> \verbatim
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> DN2 is DOUBLE PRECISION
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> d(N-2)
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> \endverbatim
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>
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> \param[out] TAU
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> \verbatim
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> TAU is DOUBLE PRECISION
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> This is the shift.
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> \endverbatim
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>
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> \param[out] TTYPE
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> \verbatim
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> TTYPE is INTEGER
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> Shift type.
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> \endverbatim
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>
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> \param[in,out] G
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> \verbatim
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> G is REAL
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> G is passed as an argument in order to save its value between
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> calls to DLASQ4.
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> \endverbatim
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Authors:
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========
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> \author Univ. of Tennessee
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> \author Univ. of California Berkeley
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> \author Univ. of Colorado Denver
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> \author NAG Ltd.
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> \date September 2012
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> \ingroup auxOTHERcomputational
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> \par Further Details:
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=====================
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>
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> \verbatim
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>
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> CNST1 = 9/16
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> \endverbatim
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>
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=====================================================================
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Subroutine */ int igraphdlasq4_(integer *i0, integer *n0, doublereal *z__,
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integer *pp, integer *n0in, doublereal *dmin__, doublereal *dmin1,
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doublereal *dmin2, doublereal *dn, doublereal *dn1, doublereal *dn2,
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doublereal *tau, integer *ttype, doublereal *g)
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{
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/* System generated locals */
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integer i__1;
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doublereal d__1, d__2;
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/* Builtin functions */
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double sqrt(doublereal);
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/* Local variables */
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doublereal s, a2, b1, b2;
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integer i4, nn, np;
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doublereal gam, gap1, gap2;
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/* -- LAPACK computational routine (version 3.4.2) --
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-- LAPACK is a software package provided by Univ. of Tennessee, --
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-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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September 2012
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=====================================================================
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A negative DMIN forces the shift to take that absolute value
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TTYPE records the type of shift.
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Parameter adjustments */
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--z__;
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/* Function Body */
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if (*dmin__ <= 0.) {
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*tau = -(*dmin__);
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*ttype = -1;
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return 0;
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}
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nn = (*n0 << 2) + *pp;
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if (*n0in == *n0) {
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/* No eigenvalues deflated. */
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if (*dmin__ == *dn || *dmin__ == *dn1) {
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b1 = sqrt(z__[nn - 3]) * sqrt(z__[nn - 5]);
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b2 = sqrt(z__[nn - 7]) * sqrt(z__[nn - 9]);
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a2 = z__[nn - 7] + z__[nn - 5];
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/* Cases 2 and 3. */
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if (*dmin__ == *dn && *dmin1 == *dn1) {
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gap2 = *dmin2 - a2 - *dmin2 * .25;
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if (gap2 > 0. && gap2 > b2) {
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gap1 = a2 - *dn - b2 / gap2 * b2;
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} else {
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gap1 = a2 - *dn - (b1 + b2);
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}
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if (gap1 > 0. && gap1 > b1) {
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/* Computing MAX */
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d__1 = *dn - b1 / gap1 * b1, d__2 = *dmin__ * .5;
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s = max(d__1,d__2);
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*ttype = -2;
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} else {
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s = 0.;
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if (*dn > b1) {
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s = *dn - b1;
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}
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if (a2 > b1 + b2) {
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/* Computing MIN */
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d__1 = s, d__2 = a2 - (b1 + b2);
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s = min(d__1,d__2);
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}
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/* Computing MAX */
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d__1 = s, d__2 = *dmin__ * .333;
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s = max(d__1,d__2);
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*ttype = -3;
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}
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} else {
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/* Case 4. */
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*ttype = -4;
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s = *dmin__ * .25;
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if (*dmin__ == *dn) {
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gam = *dn;
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a2 = 0.;
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if (z__[nn - 5] > z__[nn - 7]) {
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return 0;
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}
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b2 = z__[nn - 5] / z__[nn - 7];
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np = nn - 9;
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} else {
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np = nn - (*pp << 1);
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b2 = z__[np - 2];
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gam = *dn1;
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if (z__[np - 4] > z__[np - 2]) {
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return 0;
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}
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a2 = z__[np - 4] / z__[np - 2];
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if (z__[nn - 9] > z__[nn - 11]) {
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return 0;
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}
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b2 = z__[nn - 9] / z__[nn - 11];
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np = nn - 13;
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}
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/* Approximate contribution to norm squared from I < NN-1. */
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a2 += b2;
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i__1 = (*i0 << 2) - 1 + *pp;
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for (i4 = np; i4 >= i__1; i4 += -4) {
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if (b2 == 0.) {
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goto L20;
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}
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b1 = b2;
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if (z__[i4] > z__[i4 - 2]) {
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return 0;
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}
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b2 *= z__[i4] / z__[i4 - 2];
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a2 += b2;
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if (max(b2,b1) * 100. < a2 || .563 < a2) {
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goto L20;
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}
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/* L10: */
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}
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L20:
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a2 *= 1.05;
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/* Rayleigh quotient residual bound. */
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if (a2 < .563) {
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s = gam * (1. - sqrt(a2)) / (a2 + 1.);
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}
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}
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} else if (*dmin__ == *dn2) {
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/* Case 5. */
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*ttype = -5;
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s = *dmin__ * .25;
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/* Compute contribution to norm squared from I > NN-2. */
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np = nn - (*pp << 1);
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b1 = z__[np - 2];
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b2 = z__[np - 6];
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gam = *dn2;
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if (z__[np - 8] > b2 || z__[np - 4] > b1) {
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return 0;
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}
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a2 = z__[np - 8] / b2 * (z__[np - 4] / b1 + 1.);
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/* Approximate contribution to norm squared from I < NN-2. */
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if (*n0 - *i0 > 2) {
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b2 = z__[nn - 13] / z__[nn - 15];
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a2 += b2;
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i__1 = (*i0 << 2) - 1 + *pp;
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for (i4 = nn - 17; i4 >= i__1; i4 += -4) {
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if (b2 == 0.) {
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goto L40;
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}
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b1 = b2;
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if (z__[i4] > z__[i4 - 2]) {
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return 0;
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}
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b2 *= z__[i4] / z__[i4 - 2];
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a2 += b2;
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if (max(b2,b1) * 100. < a2 || .563 < a2) {
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goto L40;
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}
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/* L30: */
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}
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L40:
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a2 *= 1.05;
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}
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if (a2 < .563) {
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s = gam * (1. - sqrt(a2)) / (a2 + 1.);
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}
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} else {
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/* Case 6, no information to guide us. */
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if (*ttype == -6) {
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*g += (1. - *g) * .333;
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} else if (*ttype == -18) {
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*g = .083250000000000005;
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} else {
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*g = .25;
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}
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s = *g * *dmin__;
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*ttype = -6;
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}
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} else if (*n0in == *n0 + 1) {
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/* One eigenvalue just deflated. Use DMIN1, DN1 for DMIN and DN. */
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if (*dmin1 == *dn1 && *dmin2 == *dn2) {
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/* Cases 7 and 8. */
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*ttype = -7;
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s = *dmin1 * .333;
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if (z__[nn - 5] > z__[nn - 7]) {
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return 0;
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}
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b1 = z__[nn - 5] / z__[nn - 7];
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b2 = b1;
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if (b2 == 0.) {
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goto L60;
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}
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i__1 = (*i0 << 2) - 1 + *pp;
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for (i4 = (*n0 << 2) - 9 + *pp; i4 >= i__1; i4 += -4) {
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a2 = b1;
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if (z__[i4] > z__[i4 - 2]) {
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return 0;
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}
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b1 *= z__[i4] / z__[i4 - 2];
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b2 += b1;
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if (max(b1,a2) * 100. < b2) {
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goto L60;
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}
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/* L50: */
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}
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L60:
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b2 = sqrt(b2 * 1.05);
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/* Computing 2nd power */
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d__1 = b2;
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a2 = *dmin1 / (d__1 * d__1 + 1.);
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gap2 = *dmin2 * .5 - a2;
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if (gap2 > 0. && gap2 > b2 * a2) {
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/* Computing MAX */
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d__1 = s, d__2 = a2 * (1. - a2 * 1.01 * (b2 / gap2) * b2);
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s = max(d__1,d__2);
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} else {
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/* Computing MAX */
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d__1 = s, d__2 = a2 * (1. - b2 * 1.01);
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s = max(d__1,d__2);
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*ttype = -8;
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}
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} else {
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/* Case 9. */
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s = *dmin1 * .25;
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if (*dmin1 == *dn1) {
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s = *dmin1 * .5;
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}
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*ttype = -9;
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}
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} else if (*n0in == *n0 + 2) {
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/* Two eigenvalues deflated. Use DMIN2, DN2 for DMIN and DN.
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Cases 10 and 11. */
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if (*dmin2 == *dn2 && z__[nn - 5] * 2. < z__[nn - 7]) {
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*ttype = -10;
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s = *dmin2 * .333;
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if (z__[nn - 5] > z__[nn - 7]) {
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return 0;
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}
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b1 = z__[nn - 5] / z__[nn - 7];
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b2 = b1;
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if (b2 == 0.) {
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goto L80;
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}
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i__1 = (*i0 << 2) - 1 + *pp;
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for (i4 = (*n0 << 2) - 9 + *pp; i4 >= i__1; i4 += -4) {
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if (z__[i4] > z__[i4 - 2]) {
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return 0;
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}
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b1 *= z__[i4] / z__[i4 - 2];
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b2 += b1;
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if (b1 * 100. < b2) {
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goto L80;
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}
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/* L70: */
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}
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L80:
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b2 = sqrt(b2 * 1.05);
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/* Computing 2nd power */
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d__1 = b2;
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a2 = *dmin2 / (d__1 * d__1 + 1.);
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gap2 = z__[nn - 7] + z__[nn - 9] - sqrt(z__[nn - 11]) * sqrt(z__[
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nn - 9]) - a2;
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if (gap2 > 0. && gap2 > b2 * a2) {
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/* Computing MAX */
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d__1 = s, d__2 = a2 * (1. - a2 * 1.01 * (b2 / gap2) * b2);
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s = max(d__1,d__2);
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} else {
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/* Computing MAX */
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d__1 = s, d__2 = a2 * (1. - b2 * 1.01);
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s = max(d__1,d__2);
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}
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} else {
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s = *dmin2 * .25;
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*ttype = -11;
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}
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} else if (*n0in > *n0 + 2) {
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/* Case 12, more than two eigenvalues deflated. No information. */
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s = 0.;
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*ttype = -12;
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}
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*tau = s;
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return 0;
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/* End of DLASQ4 */
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} /* igraphdlasq4_ */
|
||||
|
||||
Reference in New Issue
Block a user