Add graph references
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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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/* Table of constant values */
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static integer c__1 = 1;
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static doublereal c_b11 = 1.;
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/* > \brief \b DLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matr
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ix-vector products.
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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 DLACN2 + dependencies
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> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlacn2.
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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/dlacn2.
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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/dlacn2.
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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 DLACN2( N, V, X, ISGN, EST, KASE, ISAVE )
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INTEGER KASE, N
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DOUBLE PRECISION EST
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INTEGER ISGN( * ), ISAVE( 3 )
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DOUBLE PRECISION V( * ), X( * )
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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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> DLACN2 estimates the 1-norm of a square, real matrix A.
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> Reverse communication is used for evaluating matrix-vector products.
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> \endverbatim
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Arguments:
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==========
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> \param[in] N
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> \verbatim
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> N is INTEGER
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> The order of the matrix. N >= 1.
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> \endverbatim
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>
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> \param[out] V
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> \verbatim
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> V is DOUBLE PRECISION array, dimension (N)
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> On the final return, V = A*W, where EST = norm(V)/norm(W)
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> (W is not returned).
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> \endverbatim
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>
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> \param[in,out] X
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> \verbatim
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> X is DOUBLE PRECISION array, dimension (N)
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> On an intermediate return, X should be overwritten by
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> A * X, if KASE=1,
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> A**T * X, if KASE=2,
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> and DLACN2 must be re-called with all the other parameters
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> unchanged.
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> \endverbatim
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>
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> \param[out] ISGN
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> \verbatim
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> ISGN is INTEGER array, dimension (N)
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> \endverbatim
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>
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> \param[in,out] EST
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> \verbatim
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> EST is DOUBLE PRECISION
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> On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be
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> unchanged from the previous call to DLACN2.
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> On exit, EST is an estimate (a lower bound) for norm(A).
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> \endverbatim
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>
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> \param[in,out] KASE
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> \verbatim
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> KASE is INTEGER
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> On the initial call to DLACN2, KASE should be 0.
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> On an intermediate return, KASE will be 1 or 2, indicating
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> whether X should be overwritten by A * X or A**T * X.
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> On the final return from DLACN2, KASE will again be 0.
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> \endverbatim
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>
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> \param[in,out] ISAVE
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> \verbatim
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> ISAVE is INTEGER array, dimension (3)
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> ISAVE is used to save variables between calls to DLACN2
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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 doubleOTHERauxiliary
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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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> Originally named SONEST, dated March 16, 1988.
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>
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> This is a thread safe version of DLACON, which uses the array ISAVE
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> in place of a SAVE statement, as follows:
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>
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> DLACON DLACN2
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> JUMP ISAVE(1)
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> J ISAVE(2)
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> ITER ISAVE(3)
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> \endverbatim
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> \par Contributors:
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==================
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>
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> Nick Higham, University of Manchester
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> \par References:
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================
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>
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> N.J. Higham, "FORTRAN codes for estimating the one-norm of
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> a real or complex matrix, with applications to condition estimation",
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> ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.
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>
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=====================================================================
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Subroutine */ int igraphdlacn2_(integer *n, doublereal *v, doublereal *x,
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integer *isgn, doublereal *est, integer *kase, integer *isave)
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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;
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/* Builtin functions */
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double d_sign(doublereal *, doublereal *);
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integer i_dnnt(doublereal *);
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/* Local variables */
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integer i__;
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doublereal temp;
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extern doublereal igraphdasum_(integer *, doublereal *, integer *);
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integer jlast;
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extern /* Subroutine */ int igraphdcopy_(integer *, doublereal *, integer *,
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doublereal *, integer *);
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extern integer igraphidamax_(integer *, doublereal *, integer *);
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doublereal altsgn, estold;
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/* -- LAPACK auxiliary 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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Parameter adjustments */
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--isave;
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--isgn;
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--x;
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--v;
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/* Function Body */
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if (*kase == 0) {
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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x[i__] = 1. / (doublereal) (*n);
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/* L10: */
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}
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*kase = 1;
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isave[1] = 1;
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return 0;
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}
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switch (isave[1]) {
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case 1: goto L20;
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case 2: goto L40;
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case 3: goto L70;
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case 4: goto L110;
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case 5: goto L140;
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}
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/* ................ ENTRY (ISAVE( 1 ) = 1)
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FIRST ITERATION. X HAS BEEN OVERWRITTEN BY A*X. */
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L20:
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if (*n == 1) {
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v[1] = x[1];
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*est = abs(v[1]);
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/* ... QUIT */
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goto L150;
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}
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*est = igraphdasum_(n, &x[1], &c__1);
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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x[i__] = d_sign(&c_b11, &x[i__]);
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isgn[i__] = i_dnnt(&x[i__]);
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/* L30: */
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}
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*kase = 2;
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isave[1] = 2;
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return 0;
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/* ................ ENTRY (ISAVE( 1 ) = 2)
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FIRST ITERATION. X HAS BEEN OVERWRITTEN BY TRANSPOSE(A)*X. */
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L40:
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isave[2] = igraphidamax_(n, &x[1], &c__1);
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isave[3] = 2;
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/* MAIN LOOP - ITERATIONS 2,3,...,ITMAX. */
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L50:
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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x[i__] = 0.;
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/* L60: */
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}
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x[isave[2]] = 1.;
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*kase = 1;
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isave[1] = 3;
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return 0;
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/* ................ ENTRY (ISAVE( 1 ) = 3)
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X HAS BEEN OVERWRITTEN BY A*X. */
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L70:
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igraphdcopy_(n, &x[1], &c__1, &v[1], &c__1);
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estold = *est;
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*est = igraphdasum_(n, &v[1], &c__1);
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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d__1 = d_sign(&c_b11, &x[i__]);
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if (i_dnnt(&d__1) != isgn[i__]) {
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goto L90;
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}
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/* L80: */
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}
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/* REPEATED SIGN VECTOR DETECTED, HENCE ALGORITHM HAS CONVERGED. */
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goto L120;
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L90:
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/* TEST FOR CYCLING. */
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if (*est <= estold) {
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goto L120;
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}
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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x[i__] = d_sign(&c_b11, &x[i__]);
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isgn[i__] = i_dnnt(&x[i__]);
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/* L100: */
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}
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*kase = 2;
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isave[1] = 4;
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return 0;
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/* ................ ENTRY (ISAVE( 1 ) = 4)
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X HAS BEEN OVERWRITTEN BY TRANSPOSE(A)*X. */
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L110:
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jlast = isave[2];
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isave[2] = igraphidamax_(n, &x[1], &c__1);
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if (x[jlast] != (d__1 = x[isave[2]], abs(d__1)) && isave[3] < 5) {
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++isave[3];
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goto L50;
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}
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/* ITERATION COMPLETE. FINAL STAGE. */
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L120:
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altsgn = 1.;
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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x[i__] = altsgn * ((doublereal) (i__ - 1) / (doublereal) (*n - 1) +
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1.);
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altsgn = -altsgn;
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/* L130: */
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}
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*kase = 1;
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isave[1] = 5;
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return 0;
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/* ................ ENTRY (ISAVE( 1 ) = 5)
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X HAS BEEN OVERWRITTEN BY A*X. */
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L140:
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temp = igraphdasum_(n, &x[1], &c__1) / (doublereal) (*n * 3) * 2.;
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if (temp > *est) {
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igraphdcopy_(n, &x[1], &c__1, &v[1], &c__1);
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*est = temp;
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}
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L150:
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*kase = 0;
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return 0;
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/* End of DLACN2 */
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} /* igraphdlacn2_ */
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